4 Creating a CDB: Advanced Topics
This chapter covers creating a CDB in greater detail.
- Specifying CREATE DATABASE Statement Clauses
When you execute aCREATE
DATABASE
statement, Oracle Database performs several operations. The actual operations performed depend on the clauses that you specify in theCREATE
DATABASE
statement and the initialization parameters that you have set. - Specifying Initialization Parameters
You can add or edit basic initialization parameters before you create your new database. - Managing Initialization Parameters Using a Server Parameter File
Initialization parameters for the Oracle Database have traditionally been stored in a text initialization parameter file. For better manageability, you can choose to maintain initialization parameters in a binary server parameter file that is persistent across database startup and shutdown. - Managing Application Workloads with Database Services
A database service is a named representation of one or more database instances. Services enable you to group database workloads and route a particular work request to an appropriate instance. - Managing Standard Edition High Availability for Oracle Databases
The Standard Edition High Availability feature provides protection against unplanned outages for Oracle Database Standard Edition 2 single instance databases using Oracle Clusterware. - Cloning a Database
This section describes various methods of cloning an Oracle database. - Configuring EM Express for a CDB
For a CDB, you can configure Oracle Enterprise Manager Database Express (EM Express) for the root and for each PDB by setting a global HTTPS port, or you can set a different port for every container in the CDB. - Dropping a Database
Dropping a CDB involves removing its data files, online redo logs, control files, and initialization parameter files.
Parent topic: Creating CDBs
Specifying CREATE DATABASE Statement Clauses
When you execute a CREATE
DATABASE
statement, Oracle Database performs several operations. The actual operations performed depend on the clauses that you specify in the CREATE
DATABASE
statement and the initialization parameters that you have set.
- About CREATE DATABASE Statement Clauses
You can use theCREATE DATABASE
clauses to simplify the creation and management of your database. - Protecting Your Database: Specifying Passwords for SYS and SYSTEM Users
To protect your database, specify passwords forSYS
andSYSTEM
users. - Creating a Locally Managed SYSTEM Tablespace
During database creation, create a locally managed SYSTEM tablespace. A locally managed tablespace uses a bitmap stored in each data file to manage the extents. - Specify Data File Attributes for the SYSAUX Tablespace
The SYSAUX tablespace is created by default, but you can specify its data file attributes during database creation. - Using Automatic Undo Management: Creating an Undo Tablespace
Automatic undo management uses an undo tablespace. - Creating a Default Permanent Tablespace
Oracle strongly recommends that you create a default permanent tablespace. Oracle Database assigns to this tablespace any non-SYSTEM
users for whom you do not explicitly specify a different permanent tablespace. - Creating a Default Temporary Tablespace
When you create a default temporary tablespace, Oracle Database assigns it as the temporary tablespace for users who are not explicitly assigned a temporary tablespace. - Specifying Oracle Managed Files at Database Creation
You can minimize the number of clauses and parameters that you specify in yourCREATE DATABASE
statement by using the Oracle Managed Files feature. - Supporting Bigfile Tablespaces During Database Creation
Oracle Database simplifies management of tablespaces and enables support for extremely large databases by letting you create bigfile tablespaces. - Specifying the Database Time Zone and Time Zone File
Oracle Database datetime and interval data types and time zone support make it possible to store consistent information about the time of events and transactions. - Specifying FORCE LOGGING Mode
Some data definition language statements (such asCREATE
TABLE
) allow theNOLOGGING
clause, which causes some database operations not to generate redo records in the database redo log. TheNOLOGGING
setting can speed up operations that can be easily recovered outside of the database recovery mechanisms, but it can negatively affect media recovery and standby databases.
Parent topic: Creating a CDB: Advanced Topics
About CREATE DATABASE Statement Clauses
You can use the CREATE DATABASE
clauses to simplify the creation and management of your database.
When you execute a CREATE
DATABASE
statement, Oracle Database performs at least these operations:
-
Creates the data files for the database
-
Creates the control files for the database
-
Creates the online redo logs for the database and establishes the
ARCHIVELOG
mode -
Creates the
SYSTEM
tablespace -
Creates the
SYSAUX
tablespace -
Creates the data dictionary
-
Sets the character set that stores data in the database
-
Sets the database time zone
-
Mounts and opens the database for use
Parent topic: Specifying CREATE DATABASE Statement Clauses
Protecting Your Database: Specifying Passwords for SYS and SYSTEM Users
To protect your database, specify passwords for SYS
and SYSTEM
users.
-
In the
CREATE
DATABASE
statement, include clauses that specify the password for usersSYS
andSYSTEM
.
The clauses of the CREATE
DATABASE
statement used for specifying the passwords for users SYS
and SYSTEM
are:
-
USER
SYS
IDENTIFIED
BY
password
-
USER
SYSTEM
IDENTIFIED
BY
password
When choosing a password, keep in mind that passwords are case-sensitive. Also, there may be password formatting requirements for your database.
See Also:
Oracle Database Security Guide for information about the Oracle guidelines for creating secure passwords
Parent topic: Specifying CREATE DATABASE Statement Clauses
Creating a Locally Managed SYSTEM Tablespace
During database creation, create a locally managed SYSTEM tablespace. A locally managed tablespace uses a bitmap stored in each data file to manage the extents.
-
Specify the
EXTENT MANAGEMENT LOCAL
clause in theCREATE
DATABASE
statement to create a locally managedSYSTEM
tablespace.
If you do not specify the EXTENT MANAGEMENT LOCAL
clause, then by default the database creates a dictionary-managed SYSTEM
tablespace. Dictionary-managed tablespaces are deprecated.
If you create your database with a locally managed SYSTEM
tablespace, and if you are not using Oracle Managed Files, then ensure that the following conditions are met:
-
You specify the
DEFAULT TEMPORARY TABLESPACE
clause in theCREATE DATABASE
statement. -
You include the
UNDO TABLESPACE
clause in theCREATE DATABASE
statement.
See Also:
-
Oracle Database Reference for more specific information about the use of the
DEFAULT TEMPORARY TABLESPACE
andUNDO TABLESPACE
clauses whenEXTENT MANAGEMENT LOCAL
is specified for theSYSTEM
tablespace -
Oracle Database Administrator’s Guide to learn about locally managed tablespaces
Parent topic: Specifying CREATE DATABASE Statement Clauses
Specify Data File Attributes for the SYSAUX Tablespace
The SYSAUX tablespace is created by default, but you can specify its data file attributes during database creation.
To specify data file attributes for the SYSAUX
tablespace:
-
Include the
SYSAUX DATAFILE
clause in theCREATE
DATABASE
statement.
If you include a DATAFILE
clause for the SYSTEM
tablespace, then you must specify the SYSAUX DATAFILE
clause as well, or the CREATE
DATABASE
statement will fail. This requirement does not exist if the Oracle Managed Files feature is enabled (see "Specifying Oracle Managed Files at Database Creation").
- About the SYSAUX Tablespace
TheSYSAUX
tablespace is always created at database creation.
Parent topic: Specifying CREATE DATABASE Statement Clauses
About the SYSAUX Tablespace
The SYSAUX
tablespace is always created at database creation.
The SYSAUX
tablespace serves as an auxiliary tablespace to the SYSTEM
tablespace. Because it is the default tablespace for many Oracle Database features and products that previously required their own tablespaces, it reduces the number of tablespaces required by the database. It also reduces the load on the SYSTEM
tablespace.
You can specify only data file attributes for the SYSAUX
tablespace, using the SYSAUX DATAFILE
clause in the CREATE
DATABASE
statement. Mandatory attributes of the SYSAUX
tablespace are set by Oracle Database and include:
-
PERMANENT
-
READ WRITE
-
EXTENT MANAGEMENT LOCAL
-
SEGMENT SPACE MANAGEMENT AUTO
You cannot alter these attributes with an ALTER TABLESPACE
statement, and any attempt to do so will result in an error. You cannot drop or rename the SYSAUX
tablespace.
The size of the SYSAUX
tablespace is determined by the size of the database components that occupy SYSAUX
. You can view a list of these components by querying the V$SYSAUX_OCCUPANTS
view. Based on the initial sizes of these components, the SYSAUX
tablespace must be at least 400 MB at the time of database creation. The space requirements of the SYSAUX
tablespace will increase after the database is fully deployed, depending on the nature of its use and workload.
The SYSAUX
tablespace has the same security attributes as the SYSTEM
tablespace.
See Also:
Oracle Database Administrator’s Guide to learn how to manage the SYSAUX
tablespace
Parent topic: Specify Data File Attributes for the SYSAUX Tablespace
Using Automatic Undo Management: Creating an Undo Tablespace
Automatic undo management uses an undo tablespace.
-
To enable automatic undo management, set the
UNDO_MANAGEMENT
initialization parameter toAUTO
in your initialization parameter file. Alternatively, omit this parameter so that the database defaults to automatic undo management.
In this mode, undo data is stored in an undo tablespace and is managed by Oracle Database. To define and name the undo tablespace yourself, you must include the UNDO TABLESPACE
clause in the CREATE DATABASE
statement at database creation time. If you omit this clause, and automatic undo management is enabled, then the database creates a default undo tablespace named SYS_UNDOTBS
.
Note:
If you decide to define the undo tablespace yourself, then ensure that its block size matches the highest data file block size for the database.See Also:
-
Oracle Database Administrator’s Guide for information about the creation and use of undo tablespaces
Parent topic: Specifying CREATE DATABASE Statement Clauses
Creating a Default Permanent Tablespace
Oracle strongly recommends that you create a default permanent tablespace. Oracle Database assigns to this tablespace any non-SYSTEM
users for whom you do not explicitly specify a different permanent tablespace.
To specify a default permanent tablespace for the database:
-
Include the
DEFAULT
TABLESPACE
clause in theCREATE
DATABASE
statement
If you do not specify the DEFAULT
TABLESPACE
clause, then the SYSTEM
tablespace is the default permanent tablespace for non-SYSTEM
users.
See Also:
Oracle Database SQL Language Reference for the syntax of the DEFAULT TABLESPACE
clause of CREATE DATABASE
and ALTER DATABASE
Parent topic: Specifying CREATE DATABASE Statement Clauses
Creating a Default Temporary Tablespace
When you create a default temporary tablespace, Oracle Database assigns it as the temporary tablespace for users who are not explicitly assigned a temporary tablespace.
To create a default temporary tablespace for the CDB:
-
Include the
DEFAULT TEMPORARY TABLESPACE
clause in theCREATE
DATABASE
statement.
You can explicitly assign a temporary tablespace or tablespace group to a user in the CREATE USER
statement. However, if you do not do so, and if no default temporary tablespace has been specified for the database, then by default these users are assigned the SYSTEM
tablespace as their temporary tablespace. It is not good practice to store temporary data in the SYSTEM
tablespace, and it is cumbersome to assign every user a temporary tablespace individually. Therefore, Oracle recommends that you use the DEFAULT TEMPORARY TABLESPACE
clause of CREATE DATABASE
.
Note:
When you specify a locally managed SYSTEM
tablespace, the SYSTEM
tablespace cannot be used as a temporary tablespace. In this case you must create a default temporary tablespace. This behavior is explained in "Creating a Locally Managed SYSTEM Tablespace".
See Also:
-
Oracle Database SQL Language Reference for the syntax of the
DEFAULT TEMPORARY TABLESPACE
clause ofCREATE DATABASE
andALTER DATABASE
-
Oracle Database Administrator’s Guide for information about creating and using temporary tablespaces
Parent topic: Specifying CREATE DATABASE Statement Clauses
Specifying Oracle Managed Files at Database Creation
You can minimize the number of clauses and parameters that you specify in your CREATE DATABASE
statement by using the Oracle Managed Files feature.
-
Specify either a directory or Oracle Automatic Storage Management (Oracle ASM) disk group in which your files are created and managed by Oracle Database.
By including any of the initialization parameters DB_CREATE_FILE_DEST,
DB_CREATE_ONLINE_LOG_DEST_n
, or DB_RECOVERY_FILE_DEST
in your initialization parameter file, you instruct Oracle Database to create and manage the underlying operating system files of your database. Oracle Database will automatically create and manage the operating system files for the following database structures, depending on which initialization parameters you specify and how you specify clauses in your CREATE DATABASE
statement:
-
Tablespaces and their data files
-
Temporary tablespaces and their temp files
-
Control files
-
Online redo log files
-
Archived redo log files
-
Flashback logs
-
Block change tracking files
-
RMAN backups
The following CREATE DATABASE
statement shows briefly how the Oracle Managed Files feature works, assuming you have specified required initialization parameters:
CREATE DATABASE mynewdb
USER SYS IDENTIFIED BY sys_password
USER SYSTEM IDENTIFIED BY system_password
EXTENT MANAGEMENT LOCAL
UNDO TABLESPACE undotbs1
DEFAULT TEMPORARY TABLESPACE tempts1
DEFAULT TABLESPACE users
ENABLE PLUGGABLE DATABASE
SEED
SYSTEM DATAFILES SIZE 125M AUTOEXTEND ON NEXT 10M MAXSIZE UNLIMITED
SYSAUX DATAFILES SIZE 100M;
-
The
SYSTEM
tablespace is created as a locally managed tablespace. Without theEXTENT MANAGEMENT LOCAL
clause, theSYSTEM
tablespace is created as dictionary managed, which is not recommended. -
No
DATAFILE
clause is specified, so the database creates an Oracle managed data file for theSYSTEM
tablespace. -
No
LOGFILE
clauses are included, so the database creates two Oracle managed redo log file groups. -
No
SYSAUX DATAFILE
is included, so the database creates an Oracle managed data file for theSYSAUX
tablespace. -
No
DATAFILE
subclause is specified for theUNDO TABLESPACE
andDEFAULT
TABLESPACE
clauses, so the database creates an Oracle managed data file for each of these tablespaces. -
No
TEMPFILE
subclause is specified for theDEFAULT TEMPORARY TABLESPACE
clause, so the database creates an Oracle managed temp file. -
If no
CONTROL_FILES
initialization parameter is specified in the initialization parameter file, then the database also creates an Oracle managed control file. -
If you are using a server parameter file, then the database automatically sets the appropriate initialization parameters.
See Also:
-
"Specifying a Fast Recovery Area" for information about setting initialization parameters that create a Fast Recovery Area
-
Oracle Database Administrator’s Guide for information about the Oracle Managed Files feature and how to use it
-
Oracle Automatic Storage Management Administrator's Guide for information about Automatic Storage Management
-
Parent topic: Specifying CREATE DATABASE Statement Clauses
Supporting Bigfile Tablespaces During Database Creation
Oracle Database simplifies management of tablespaces and enables support for extremely large databases by letting you create bigfile tablespaces.
Bigfile tablespaces can contain only one file, but that file can have up to 4G blocks. The maximum number of data files in an Oracle Database is limited (usually to 64K files). Therefore, bigfile tablespaces can significantly enhance the storage capacity of an Oracle Database.
This section discusses the clauses of the CREATE DATABASE
statement that let you include support for bigfile tablespaces.
- Specifying the Default Tablespace Type
TheSET DEFAULT...TABLESPACE
clause of theCREATE DATABASE
statement determines the default type of tablespace for this database in subsequentCREATE TABLESPACE
statements. - Overriding the Default Tablespace Type
TheSYSTEM
andSYSAUX
tablespaces are always created with the default tablespace type. However, you optionally can explicitly override the default tablespace type for theUNDO
andDEFAULT TEMPORARY
tablespace during theCREATE DATABASE
operation.
See Also:
Oracle Database Administrator’s Guide for more information about bigfile tablespaces
Parent topic: Specifying CREATE DATABASE Statement Clauses
Specifying the Default Tablespace Type
The SET DEFAULT...TABLESPACE
clause of the CREATE DATABASE
statement determines the default type of tablespace for this database in subsequent CREATE TABLESPACE
statements.
-
Specify either
SET DEFAULT BIGFILE TABLESPACE
orSET DEFAULT SMALLFILE TABLESPACE
.
If you omit this clause, then the default is a smallfile tablespace, which is the traditional type of Oracle Database tablespace. A smallfile tablespace can contain up to 1022 files with up to 4M blocks each.
The use of bigfile tablespaces further enhances the Oracle Managed Files feature, because bigfile tablespaces make data files completely transparent for users. SQL syntax for the ALTER TABLESPACE
statement has been extended to allow you to perform operations on tablespaces, rather than the underlying data files.
The CREATE DATABASE
statement shown in "Specifying Oracle Managed Files at Database Creation" can be modified as follows to specify that the default type of tablespace is a bigfile tablespace:
CREATE DATABASE mynewdb
USER SYS IDENTIFIED BY sys_password
USER SYSTEM IDENTIFIED BY system_password
SET DEFAULT BIGFILE TABLESPACE
UNDO TABLESPACE undotbs1
DEFAULT TEMPORARY TABLESPACE tempts1
ENABLE PLUGGABLE DATABASE
SEED
SYSTEM DATAFILES SIZE 125M AUTOEXTEND ON NEXT 10M MAXSIZE UNLIMITED
SYSAUX DATAFILES SIZE 100M;
To dynamically change the default tablespace type after database creation, use the SET DEFAULT TABLESPACE
clause of the ALTER DATABASE
statement:
ALTER DATABASE SET DEFAULT BIGFILE TABLESPACE;
You can determine the current default tablespace type for the database by querying the DATABASE_PROPERTIES
data dictionary view as follows:
SELECT PROPERTY_VALUE FROM DATABASE_PROPERTIES
WHERE PROPERTY_NAME = 'DEFAULT_TBS_TYPE';
Parent topic: Supporting Bigfile Tablespaces During Database Creation
Overriding the Default Tablespace Type
The SYSTEM
and SYSAUX
tablespaces are always created with the default tablespace type. However, you optionally can explicitly override the default tablespace type for the UNDO
and DEFAULT TEMPORARY
tablespace during the CREATE DATABASE
operation.
-
Specify an
UNDO TABLESPACE
clause or aDEFAULT TEMPORARY TABLESPACE
clause that overrides the default tablespace type.
For example, you can create a bigfile UNDO
tablespace in a database with the default tablespace type of smallfile as follows:
CREATE DATABASE mynewdb
...
BIGFILE UNDO TABLESPACE undotbs1
DATAFILE '/u01/oracle/oradata/mynewdb/undotbs01.dbf'
SIZE 200M REUSE AUTOEXTEND ON MAXSIZE UNLIMITED;
You can create a smallfile DEFAULT
TEMPORARY
tablespace in a database with the default tablespace type of bigfile as follows:
CREATE DATABASE mynewdb
SET DEFAULT BIGFILE TABLESPACE
...
SMALLFILE DEFAULT TEMPORARY TABLESPACE tempts1
TEMPFILE '/u01/oracle/oradata/mynewdb/temp01.dbf'
SIZE 20M REUSE
...
Parent topic: Supporting Bigfile Tablespaces During Database Creation
Specifying the Database Time Zone and Time Zone File
Oracle Database datetime and interval data types and time zone support make it possible to store consistent information about the time of events and transactions.
- Setting the Database Time Zone
You can set the database time zone with theSET TIME_ZONE
clause of theCREATE DATABASE
statement. - About the Database Time Zone Files
Two time zone files are included in a subdirectory of the Oracle home directory. The time zone files contain the valid time zone names. - Specifying the Database Time Zone File
All databases that share information must use the same time zone data file.
Parent topic: Specifying CREATE DATABASE Statement Clauses
Setting the Database Time Zone
You can set the database time zone with the SET TIME_ZONE
clause of the CREATE DATABASE
statement.
-
Set the database time zone when the database is created by using the
SET TIME_ZONE
clause of theCREATE DATABASE
statement.
If you do not set the database time zone, then it defaults to the time zone of the host operating system.
You can change the database time zone for a session by using the SET TIME_ZONE
clause of the ALTER SESSION
statement.
See Also:
Oracle Database Globalization Support Guide for more information about setting the database time zone
Parent topic: Specifying the Database Time Zone and Time Zone File
About the Database Time Zone Files
Two time zone files are included in a subdirectory of the Oracle home directory. The time zone files contain the valid time zone names.
The following information is also included for each time zone:
-
Offset from Coordinated Universal Time (UTC)
-
Transition times for Daylight Saving Time
-
Abbreviations for standard time and Daylight Saving Time
The default time zone file is ORACLE_HOME/oracore/zoneinfo/timezlrg_11.dat. A smaller time zone file with fewer time zones can be found in ORACLE_HOME/oracore/zoneinfo/timezone_11.dat.
To view the time zone names in the file being used by your database, use the following query:
SELECT * FROM V$TIMEZONE_NAMES;
See Also:
Oracle Database Globalization Support Guide for more information about managing and selecting time zone files
Parent topic: Specifying the Database Time Zone and Time Zone File
Specifying the Database Time Zone File
All databases that share information must use the same time zone data file.
The database server always uses the large time zone file by default.
To use the small time zone file on the client and know that all your data will refer only to regions in the small file:
-
Set the
ORA_TZFILE
environment variable on the client to the full path name of the timezoneversion
.dat file on the client, whereversion
matches the time zone file version that is being used by the database server.
If you are already using the default larger time zone file on the client, then it is not practical to change to the smaller time zone file, because the database may contain data with time zones that are not part of the smaller file.
Parent topic: Specifying the Database Time Zone and Time Zone File
Specifying FORCE LOGGING Mode
Some data definition language statements (such as CREATE
TABLE
) allow the NOLOGGING
clause, which causes some database operations not to generate redo records in the database redo log. The NOLOGGING
setting can speed up operations that can be easily recovered outside of the database recovery mechanisms, but it can negatively affect media recovery and standby databases.
Oracle Database lets you force the writing of redo records even when NOLOGGING
has been specified in DDL statements. The database never generates redo records for temporary tablespaces and temporary segments, so forced logging has no affect for objects.
- Using the FORCE LOGGING Clause
You can force the writing of redo records even whenNOLOGGING
is specified in DDL statements. - Performance Considerations of FORCE LOGGING Mode
FORCE LOGGING
mode results in some performance degradation.
See Also:
Oracle Database SQL Language Reference for information about operations that can be done in NOLOGGING
mode
Parent topic: Specifying CREATE DATABASE Statement Clauses
Using the FORCE LOGGING Clause
You can force the writing of redo records even when NOLOGGING
is specified in DDL statements.
To put the database into FORCE LOGGING
mode:
-
Include the
FORCE LOGGING
clause in theCREATE DATABASE
statement.
If you do not specify this clause, then the database is not placed into FORCE LOGGING
mode.
Use the ALTER DATABASE
statement to place the database into FORCE LOGGING
mode after database creation. This statement can take a considerable time for completion, because it waits for all unlogged direct writes to complete.
You can cancel FORCE LOGGING
mode using the following SQL statement:
ALTER DATABASE NO FORCE LOGGING;
Independent of specifying FORCE LOGGING
for the database, you can selectively specify FORCE LOGGING
or NO FORCE LOGGING
at the tablespace level. However, if FORCE LOGGING
mode is in effect for the database, it takes precedence over the tablespace setting. If it is not in effect for the database, then the individual tablespace settings are enforced. Oracle recommends that either the entire database is placed into FORCE LOGGING
mode, or individual tablespaces be placed into FORCE LOGGING
mode, but not both.
The FORCE LOGGING
mode is a persistent attribute of the database. That is, if the database is shut down and restarted, it remains in the same logging mode. However, if you re-create the control file, the database is not restarted in the FORCE LOGGING
mode unless you specify the FORCE LOGGING
clause in the CREATE CONTROL FILE
statement.
See Also:
Oracle Database Administrator’s Guide for information about using the FORCE LOGGING
clause for tablespace creation.
Parent topic: Specifying FORCE LOGGING Mode
Performance Considerations of FORCE LOGGING Mode
FORCE LOGGING
mode results in some performance degradation.
If the primary reason for specifying FORCE LOGGING
is to ensure complete media recovery, and there is no standby database active, then consider the following:
-
How many media failures are likely to happen?
-
How serious is the damage if unlogged direct writes cannot be recovered?
-
Is the performance degradation caused by forced logging tolerable?
If the database is running in NOARCHIVELOG
mode, then generally there is no benefit to placing the database in FORCE LOGGING
mode. Media recovery is not possible in NOARCHIVELOG
mode, so if you combine it with FORCE LOGGING
, the result may be performance degradation with little benefit.
Starting with Oracle Database 18c, the following two new nologging clauses are introduced, which enable non-logged operations to be carried out and have Active Data Guard standby databases receive all the data, thus preventing performance degradation caused by large redo log generation by the FORCE LOGGING
mode:
-
STANDBY NOLOGGING FOR DATA AVAILABILITY
-
STANDBY NOLOGGING FOR LOAD PERFORMANCE
See Also:
Oracle Data Guard Concepts and Administration for more information about these STANDBY NOLOGGING
clauses
Parent topic: Specifying FORCE LOGGING Mode
Specifying Initialization Parameters
You can add or edit basic initialization parameters before you create your new database.
- About Initialization Parameters and Initialization Parameter Files
When an Oracle instance starts, it reads initialization parameters from an initialization parameter file. This file must at a minimum specify theDB_NAME
parameter. All other parameters have default values. - Determining the Global Database Name
The global database name consists of the user-specified local database name and the location of the database within a network structure. - Specifying a Fast Recovery Area
The Fast Recovery Area is a location in which Oracle Database can store and manage files related to backup and recovery. It is distinct from the database area, which is a location for the current database files (data files, control files, and online redo logs). - Specifying Control Files
Every database has a control file, which contains entries that describe the structure of the database (such as its name, the timestamp of its creation, and the names and locations of its data files and redo files). TheCONTROL_FILES
initialization parameter specifies one or more names of control files, separated by commas. - Specifying Database Block Sizes
TheDB_BLOCK_SIZE
initialization parameter specifies the standard block size for the database. - Specifying the Maximum Number of Processes
ThePROCESSES
initialization parameter determines the maximum number of operating system processes that can be connected to Oracle Database concurrently. - Specifying the DDL Lock Timeout
You can specify the amount of time that blocking DDL statements wait for locks. - Specifying the Method of Undo Space Management
Every Oracle Database must have a method of maintaining information that is used to undo changes to the database. Such information consists of records of the actions of transactions, primarily before they are committed. Collectively these records are called undo data. - Specifying the Database Compatibility Level
TheCOMPATIBLE
initialization parameter controls the database compatibility level. - Setting the License Parameter
If you use named user licensing, Oracle Database can help you enforce this form of licensing. You can set a limit on the number of users created in the database. Once this limit is reached, you cannot create more users.
See Also:
-
Oracle Database Administrator’s Guide for a discussion of the initialization parameters that pertain to memory management
-
Oracle Database Reference for descriptions of all initialization parameters including their default settings
Parent topic: Creating a CDB: Advanced Topics
About Initialization Parameters and Initialization Parameter Files
When an Oracle instance starts, it reads initialization parameters from an initialization parameter file. This file must at a minimum specify the DB_NAME
parameter. All other parameters have default values.
The initialization parameter file can be either a read-only text file, a PFILE
, or a read/write binary file.
The binary file is called a server parameter file. A server parameter file enables you to change initialization parameters with ALTER SYSTEM
commands and to persist the changes across a shutdown and startup. It also provides a basis for self-tuning by Oracle Database. For these reasons, it is recommended that you use a server parameter file. You can create one manually from your edited text initialization file, or automatically by using Database Configuration Assistant (DBCA) to create your database.
Before you manually create a server parameter file, you can start an instance with a text initialization parameter file. Upon startup, the Oracle instance first searches for a server parameter file in a default location, and if it does not find one, searches for a text initialization parameter file. You can also override an existing server parameter file by naming a text initialization parameter file as an argument of the STARTUP
command.
Default file names and locations for the text initialization parameter file are shown in the following table:
Platform | Default Name | Default Location |
---|---|---|
UNIX and Linux |
For example, the initialization parameter file for the
|
ORACLE_HOME/ |
Windows |
|
ORACLE_HOME\ |
If you are creating an Oracle database for the first time, Oracle suggests that you minimize the number of parameter values that you alter. As you become more familiar with your database and environment, you can dynamically tune many initialization parameters using the ALTER SYSTEM
statement. If you are using a text initialization parameter file, then your changes are effective only for the current instance. To make them permanent, you must update them manually in the initialization parameter file, or they will be lost over the next shutdown and startup of the database. If you are using a server parameter file, then initialization parameter file changes made by the ALTER SYSTEM
statement can persist across shutdown and startup.
- Sample Initialization Parameter File
Oracle Database provides generally appropriate values in a sample text initialization parameter file. You can edit these Oracle-supplied initialization parameters and add others, depending upon your configuration and options and how you plan to tune the database. - Text Initialization Parameter File Format
The text initialization parameter file specifies the values of parameters in name/value pairs. - Expressions in Initialization Parameter Settings
Set the value of an initialization parameter to the desired numeric value, text value, or expression.
See Also:
-
"Determining the Global Database Name" for information about the
DB_NAME
parameter -
"Managing Initialization Parameters Using a Server Parameter File"
Parent topic: Specifying Initialization Parameters
Sample Initialization Parameter File
Oracle Database provides generally appropriate values in a sample text initialization parameter file. You can edit these Oracle-supplied initialization parameters and add others, depending upon your configuration and options and how you plan to tune the database.
The sample text initialization parameter file is named init.ora
and is found in the following location on most platforms:
ORACLE_HOME/dbs
The following is the content of the sample file:
##############################################################################
# Example INIT.ORA file
#
# This file is provided by Oracle Corporation to help you start by providing
# a starting point to customize your RDBMS installation for your site.
#
# NOTE: The values that are used in this file are only intended to be used
# as a starting point. You may want to adjust/tune those values to your
# specific hardware and needs. You may also consider using Database
# Configuration Assistant tool (DBCA) to create INIT file and to size your
# initial set of tablespaces based on the user input.
###############################################################################
# Change '<ORACLE_BASE>' to point to the oracle base (the one you specify at
# install time)
db_name='ORCL'
memory_target=1G
processes = 150
db_block_size=8192
db_domain=''
db_recovery_file_dest='<ORACLE_BASE>/flash_recovery_area'
db_recovery_file_dest_size=2G
diagnostic_dest='<ORACLE_BASE>'
dispatchers='(PROTOCOL=TCP) (SERVICE=ORCLXDB)'
open_cursors=300
remote_login_passwordfile='EXCLUSIVE'
undo_tablespace='UNDOTBS1'
# You may want to ensure that control files are created on separate physical
# devices
control_files = (ora_control1, ora_control2)
compatible ='12.0.0'
enable_pluggable_database=TRUE
Text Initialization Parameter File Format
The text initialization parameter file specifies the values of parameters in name/value pairs.
The text initialization parameter file (PFILE) must contain name/value pairs in one of the following forms:
-
For parameters that accept only a single value:
parameter_name=value
-
For parameters that accept one or more values (such as the
CONTROL_FILES
parameter):parameter_name=(value[,value] ...)
Parameter values of type string must be enclosed in single quotes ('). Case (upper or lower) in file names is significant only if case is significant on the host operating system.
For parameters that accept multiple values, to enable you to easily copy and paste name/value pairs from the alert log, you can repeat a parameter on multiple lines, where each line contains a different value.
control_files='/u01/app/oracle/oradata/orcl/control01.ctl' control_files='/u01/app/oracle/oradata/orcl/control02.ctl' control_files='/u01/app/oracle/oradata/orcl/control03.ctl'
If you repeat a parameter that does not accept multiple values, then only the last value specified takes effect.
See Also:
-
Oracle Database Administrator’s Guide to learn about the alert log
-
Oracle Database Reference for more information about the content and syntax of the text initialization parameter file
Expressions in Initialization Parameter Settings
Set the value of an initialization parameter to the desired numeric value, text value, or expression.
Starting with Oracle Database Release 21c, you can use expressions when setting the value of initialization parameters. The expressions can contain other initialization parameters and one or more of the following:
- arithmetic operators (+, -, *, /)
- environment variables
MIN
orMAX
function
Examples:
SGA_TARGET = SYSTEM_MEMORY * 0.4
PARALLEL_MAX_SERVERS = MAX(100, PROCESSES * 0.4)
DB_CREATE_FILE_DEST=$ORACLE_HOME/oracle/database_files
Determining the Global Database Name
The global database name consists of the user-specified local database name and the location of the database within a network structure.
-
Set the
DB_NAME
andDB_DOMAIN
initialization parameters.
The DB_NAME
initialization parameter determines the local name component of the database name, and the DB_DOMAIN
parameter, which is optional, indicates the domain (logical location) within a network structure. The combination of the settings for these two parameters must form a database name that is unique within a network.
For example, to create a database with a global database name of test.us.example.com
, edit the parameters of the new parameter file as follows:
DB_NAME = test DB_DOMAIN = us.example.com
You can rename the GLOBAL_NAME
of your database using the ALTER DATABASE RENAME GLOBAL_NAME
statement. However, you must also shut down and restart the database after first changing the DB_NAME
and DB_DOMAIN
initialization parameters and recreating the control files. Recreating the control files is easily accomplished with the command ALTER
DATABASE
BACKUP
CONTROLFILE
TO
TRACE
. See Oracle Database Backup and Recovery User's Guide for more information.
- DB_NAME Initialization Parameter
TheDB_NAME
initialization parameter specifies a database identifier. - DB_DOMAIN Initialization Parameter
In a distributed database system, theDB_DOMAIN
initialization parameter specifies the logical location of the database within the network structure.
See Also:
Oracle Database Utilities for information about using the DBNEWID
utility, which is another means of changing a database name
Parent topic: Specifying Initialization Parameters
DB_NAME Initialization Parameter
The DB_NAME
initialization parameter specifies a database identifier.
DB_NAME
must be set to a text string of no more than 8 characters. The database name must start with an alphabetic character. During database creation, the name provided for DB_NAME
is recorded in the data files, redo log files, and control file of the database. If during database instance startup the value of the DB_NAME
parameter (in the parameter file) and the database name in the control file are different, then the database does not start.
Parent topic: Determining the Global Database Name
DB_DOMAIN Initialization Parameter
In a distributed database system, the DB_DOMAIN
initialization parameter specifies the logical location of the database within the network structure.
DB_DOMAIN
is a text string that specifies the network domain where the database is created. If the database you are about to create will ever be part of a distributed database system, then give special attention to this initialization parameter before database creation. This parameter is optional.
See Also:
Oracle Database Administrator’s Guide for more information about distributed databases
Parent topic: Determining the Global Database Name
Specifying a Fast Recovery Area
The Fast Recovery Area is a location in which Oracle Database can store and manage files related to backup and recovery. It is distinct from the database area, which is a location for the current database files (data files, control files, and online redo logs).
Specify the Fast Recovery Area with the following initialization parameters:
-
DB_RECOVERY_FILE_DEST
: Location of the Fast Recovery Area. This can be a directory, file system, or Automatic Storage Management (Oracle ASM) disk group.In an Oracle Real Application Clusters (Oracle RAC) environment, this location must be on a cluster file system, Oracle ASM disk group, or a shared directory configured through NFS.
-
DB_RECOVERY_FILE_DEST_SIZE
: Specifies the maximum total bytes to be used by the Fast Recovery Area. This initialization parameter must be specified beforeDB_RECOVERY_FILE_DEST
is enabled.
In an Oracle RAC environment, the settings for these two parameters must be the same on all instances.
You cannot enable these parameters if you have set values for the LOG_ARCHIVE_DEST
and LOG_ARCHIVE_DUPLEX_DEST
parameters. You must disable those parameters before setting up the Fast Recovery Area. You can instead set values for the LOG_ARCHIVE_DEST_
n
parameters.
Oracle recommends using a Fast Recovery Area, because it can simplify backup and recovery operations for your database.
See Also:
Oracle Database Backup and Recovery User's Guide to learn how to create and use a Fast Recovery Area
Parent topic: Specifying Initialization Parameters
Specifying Control Files
Every database has a control file, which contains entries that describe the structure of the database (such as its name, the timestamp of its creation, and the names and locations of its data files and redo files). The CONTROL_FILES
initialization parameter specifies one or more names of control files, separated by commas.
-
Set the
CONTROL_FILES
initialization parameter.
When you execute the CREATE DATABASE
statement, the control files listed in the CONTROL_FILES
parameter are created.
If you do not include CONTROL_FILES
in the initialization parameter file, then Oracle Database creates a control file in the same directory as the initialization parameter file, using a default operating system–dependent file name. If you have enabled Oracle Managed Files, the database creates Oracle managed control files.
If you want the database to create new operating system files when creating database control files, the file names listed in the CONTROL_FILES
parameter must not match any file names that currently exist on your system. If you want the database to reuse or overwrite existing files when creating database control files, ensure that the file names listed in the CONTROL_FILES
parameter match the file names that are to be reused, and include a CONTROLFILE REUSE
clause in the CREATE DATABASE
statement.
Oracle strongly recommends you use at least two control files stored on separate physical disk drives for each database.
Specifying Database Block Sizes
The DB_BLOCK_SIZE
initialization parameter specifies the standard block size for the database.
-
Set the
DB_BLOCK_SIZE
initialization parameter.
This block size is used for the SYSTEM
tablespace and by default in other tablespaces. Oracle Database can support up to four additional nonstandard block sizes.
- DB_BLOCK_SIZE Initialization Parameter
The most commonly used block size should be picked as the standard block size. In many cases, this is the only block size that you must specify. - Nonstandard Block Sizes
You can create tablespaces of nonstandard block sizes.
Parent topic: Specifying Initialization Parameters
DB_BLOCK_SIZE Initialization Parameter
The most commonly used block size should be picked as the standard block size. In many cases, this is the only block size that you must specify.
-
Set the
DB_BLOCK_SIZE
initialization parameter.
Typically, DB_BLOCK_SIZE
is set to either 4K or 8K. If you do not set a value for this parameter, then the default data block size is operating system specific, which is generally adequate.
You cannot change the block size after database creation except by re-creating the database. If the database block size is different from the operating system block size, then ensure that the database block size is a multiple of the operating system block size. For example, if your operating system block size is 2K (2048 bytes), the following setting for the DB_BLOCK_SIZE
initialization parameter is valid:
DB_BLOCK_SIZE=4096
A larger data block size provides greater efficiency in disk and memory I/O (access and storage of data). Therefore, consider specifying a block size larger than your operating system block size if the following conditions exist:
-
Oracle Database is on a large computer system with a large amount of memory and fast disk drives. For example, databases controlled by mainframe computers with vast hardware resources typically use a data block size of 4K or greater.
-
The operating system that runs Oracle Database uses a small operating system block size. For example, if the operating system block size is 1K and the default data block size matches this, the database may be performing an excessive amount of disk I/O during normal operation. For best performance in this case, a database block should consist of multiple operating system blocks.
See Also:
Your operating system specific Oracle documentation for details about the default block size.
Parent topic: Specifying Database Block Sizes
Nonstandard Block Sizes
You can create tablespaces of nonstandard block sizes.
To create tablespaces of nonstandard block sizes:
-
Specify the
BLOCKSIZE
clause in aCREATE TABLESPACE
statement.
These nonstandard block sizes can have any of the following power-of-two values: 2K, 4K, 8K, 16K or 32K. Platform-specific restrictions regarding the maximum block size apply, so some of these sizes may not be allowed on some platforms.
To use nonstandard block sizes, you must configure subcaches within the buffer cache area of the SGA memory for all of the nonstandard block sizes that you intend to use. The initialization parameters used for configuring these subcaches are described in Oracle Database Administrator’s Guide.
The ability to specify multiple block sizes for your database is especially useful if you are transporting tablespaces between databases. You can, for example, transport a tablespace that uses a 4K block size from an OLTP environment to a data warehouse environment that uses a standard block size of 8K.
Note:
A 32K block size is valid only on 64-bit platforms.
Caution:
Oracle recommends against specifying a 2K block size when 4K sector size disks are in use, because performance degradation can occur. For an explanation, see Oracle Database Administrator’s Guide.
Parent topic: Specifying Database Block Sizes
Specifying the Maximum Number of Processes
The PROCESSES
initialization parameter determines the maximum number of operating system processes that can be connected to Oracle Database concurrently.
-
Set the
PROCESSES
initialization parameter.
The value of this parameter must be a minimum of one for each background process plus one for each user process. The number of background processes will vary according the database features that you are using. For example, if you are using Advanced Queuing or the file mapping feature, then you will have additional background processes. If you are using Automatic Storage Management, then add three additional processes for the database instance.
If you plan on running 50 user processes, a good estimate would be to set the PROCESSES
initialization parameter to 70.
Parent topic: Specifying Initialization Parameters
Specifying the DDL Lock Timeout
You can specify the amount of time that blocking DDL statements wait for locks.
A data definition language (DDL) statement is either nonblocking or blocking, and both types of DDL statements require exclusive locks on internal structures. If these locks are unavailable when a DDL statement runs, then nonblocking and blocking DDL statements behave differently:
-
Nonblocking DDL waits until every concurrent DML transaction that references the object affected by the DDL either commits or rolls back.
-
Blocking DDL fails, though it might have succeeded if it had been executed subseconds later when the locks become available.
To enable blocking DDL statements to wait for locks, specify a DDL lock timeout—the number of seconds a DDL command waits for its required locks before failing.
-
To specify a DDL lock timeout, set the
DDL_LOCK_TIMEOUT
parameter.
The permissible range of values for DDL_LOCK_TIMEOUT
is 0 to 1,000,000. The default is 0. You can set DDL_LOCK_TIMEOUT
at the system level, or at the session level with an ALTER
SESSION
statement.
Note:
The DDL_LOCK_TIMEOUT
parameter does not affect nonblocking DDL statements.
Specifying the Method of Undo Space Management
Every Oracle Database must have a method of maintaining information that is used to undo changes to the database. Such information consists of records of the actions of transactions, primarily before they are committed. Collectively these records are called undo data.
To set up an environment for automatic undo management using an undo tablespace.
-
Set the
UNDO_MANAGEMENT
initialization parameter toAUTO
, which is the default.
- UNDO_MANAGEMENT Initialization Parameter
TheUNDO_MANAGEMENT
initialization parameter determines whether an instance starts in automatic undo management mode, which stores undo in an undo tablespace. Set this parameter toAUTO
to enable automatic undo management mode.AUTO
is the default if the parameter is omitted or is null. - UNDO_TABLESPACE Initialization Parameter
TheUNDO_TABLESPACE
initialization parameter enables you to override that default undo tablespace for an instance.
See Also:
Parent topic: Specifying Initialization Parameters
UNDO_MANAGEMENT Initialization Parameter
The UNDO_MANAGEMENT
initialization parameter determines whether an instance starts in automatic undo management mode, which stores undo in an undo tablespace. Set this parameter to AUTO
to enable automatic undo management mode. AUTO
is the default if the parameter is omitted or is null.
Parent topic: Specifying the Method of Undo Space Management
UNDO_TABLESPACE Initialization Parameter
The UNDO_TABLESPACE
initialization parameter enables you to override that default undo tablespace for an instance.
When an instance starts up in automatic undo management mode, it attempts to select an undo tablespace for storage of undo data. If the database was created in automatic undo management mode, then the default undo tablespace (either the system-created SYS_UNDOTBS
tablespace or the user-specified undo tablespace) is the undo tablespace used at instance startup. You can override this default for the instance by specifying a value for the UNDO_TABLESPACE
initialization parameter. This parameter is especially useful for assigning a particular undo tablespace to an instance in an Oracle Real Application Clusters environment.
If no undo tablespace is specified by the UNDO_TABLESPACE
initialization parameter, then the first available undo tablespace in the database is chosen. If no undo tablespace is available, then the instance starts without an undo tablespace, and undo data is written to the SYSTEM
tablespace. You should avoid running in this mode.
Note:
When using the CREATE
DATABASE
statement to create a database, do not include an UNDO_TABLESPACE
parameter in the initialization parameter file. Instead, include an UNDO
TABLESPACE
clause in the CREATE
DATABASE
statement.
Parent topic: Specifying the Method of Undo Space Management
Specifying the Database Compatibility Level
The COMPATIBLE
initialization parameter controls the database compatibility level.
-
Set the
COMPATIBLE
initialization parameter to a release number.
- About the COMPATIBLE Initialization Parameter
TheCOMPATIBLE
initialization parameter enables or disables the use of features in the database that affect file format on disk. For example, if you create an Oracle Database 19c database, but specifyCOMPATIBLE=12.0.0
in the initialization parameter file, then features that require Oracle Database 19c compatibility generate an error if you try to use them. Such a database is said to be at the 12.0.0 compatibility level.
Parent topic: Specifying Initialization Parameters
About the COMPATIBLE Initialization Parameter
The COMPATIBLE
initialization parameter enables or disables the use of features in the database that affect file format on disk. For example, if you create an Oracle Database 19c database, but specify COMPATIBLE=12.0.0
in the initialization parameter file, then features that require Oracle Database 19c compatibility generate an error if you try to use them. Such a database is said to be at the 12.0.0 compatibility level.
You can advance the compatibility level of your database by changing the COMPATIBLE
initialization parameter. If you do, then there is no way to start the database using a lower compatibility level setting, except by doing a point-in-time recovery to a time before the compatibility was advanced.
The default value for the COMPATIBLE
parameter is the release number of the most recent major release.
Note:
-
When you set this parameter in a server parameter file (SPFILE) using the
ALTER SYSTEM
statement, you must specifySCOPE=SPFILE
, and you must restart the database for the change to take effect. -
The
COMPATIBLE
initialization parameter must be specified as at least three decimal numbers separated by a dot, such as19.0.0
.
See Also:
-
Oracle Database Upgrade Guide for a detailed discussion of database compatibility and the
COMPATIBLE
initialization parameter -
Oracle Database Backup and Recovery User's Guide for information about point-in-time recovery of your database
Parent topic: Specifying the Database Compatibility Level
Setting the License Parameter
If you use named user licensing, Oracle Database can help you enforce this form of licensing. You can set a limit on the number of users created in the database. Once this limit is reached, you cannot create more users.
Note:
This mechanism assumes that each person accessing the database has a unique user name and that no people share a user name. Therefore, so that named user licensing can help you ensure compliance with your Oracle license agreement, do not allow multiple users to log in using the same user name.
To limit the number of users created in a database, set the LICENSE_MAX_USERS
initialization parameter in the database initialization parameter file.
The following example sets the LICENSE_MAX_USERS
initialization parameter:
LICENSE_MAX_USERS = 200
Note:
Oracle no longer offers licensing by the number of concurrent sessions. Therefore the LICENSE_MAX_SESSIONS
and LICENSE_SESSIONS_WARNING
initialization parameters are no longer needed and have been deprecated.
Parent topic: Specifying Initialization Parameters
Managing Initialization Parameters Using a Server Parameter File
Initialization parameters for the Oracle Database have traditionally been stored in a text initialization parameter file. For better manageability, you can choose to maintain initialization parameters in a binary server parameter file that is persistent across database startup and shutdown.
- What Is a Server Parameter File?
A server parameter file can be thought of as a repository for initialization parameters that is maintained on the system running the Oracle Database server. It is, by design, a server-side initialization parameter file. - Migrating to a Server Parameter File
If you are currently using a text initialization parameter file, then you can migrate to a server parameter file. - Server Parameter File Default Names and Locations
Oracle recommends that you allow the database to give the SPFILE the default name and store it in the default location. This eases administration of your database. For example, theSTARTUP
command assumes this default location to read the SPFILE. - Creating a Server Parameter File
You use theCREATE SPFILE
statement to create a server parameter file. You must have theSYSDBA
,SYSOPER
, orSYSBACKUP
administrative privilege to execute this statement. - The SPFILE Initialization Parameter
TheSPFILE
initialization parameter contains the name of the current server parameter file. - Changing Initialization Parameter Values
You can change initialization parameter values to affect the operation of a database instance. - Clearing Initialization Parameter Values
You can use theALTER SYSTEM RESET
statement to clear an initialization parameter value. When you do so, the initialization parameter value is changed to its default value or its startup value. - Exporting the Server Parameter File
You can use theCREATE PFILE
statement to export a server parameter file (SPFILE) to a text initialization parameter file. - Backing Up the Server Parameter File
You can create a backup of your server parameter file (SPFILE) by exporting it. If the backup and recovery strategy for your database is implemented using Recovery Manager (RMAN), then you can use RMAN to create a backup of the SPFILE. The SPFILE is backed up automatically by RMAN when you back up your database, but RMAN also enables you to specifically create a backup of the currently active SPFILE. - Recovering a Lost or Damaged Server Parameter File
You can recover the server parameter file (SPFILE). If your server parameter file (SPFILE) becomes lost or corrupted, then the current instance may fail, or the next attempt at starting the database instance may fail. - Methods for Viewing Parameter Settings
You can view parameter settings using several different methods.
Parent topic: Creating a CDB: Advanced Topics
What Is a Server Parameter File?
A server parameter file can be thought of as a repository for initialization parameters that is maintained on the system running the Oracle Database server. It is, by design, a server-side initialization parameter file.
Initialization parameters stored in a server parameter file are persistent, in that any changes made to the parameters while an instance is running can persist across instance shutdown and startup. This arrangement eliminates the need to manually update initialization parameters to make persistent any changes effected by ALTER SYSTEM
statements. It also provides a basis for self-tuning by the Oracle Database server.
A server parameter file is initially built from a text initialization parameter file using the CREATE SPFILE
statement. (It can also be created directly by the Database Configuration Assistant.) The server parameter file is a binary file that cannot be edited using a text editor. Oracle Database provides other interfaces for viewing and modifying parameter settings in a server parameter file.
Note:
Although you can open the binary server parameter file with a text editor and view its text, do not manually edit it. Doing so will corrupt the file. You will not be able to start your instance, and if the instance is running, it could fail.
When you issue a STARTUP
command with no PFILE
clause, the Oracle instance searches an operating system–specific default location for a server parameter file from which to read initialization parameter settings. If no server parameter file is found, the instance searches for a text initialization parameter file. If a server parameter file exists but you want to override it with settings in a text initialization parameter file, you must specify the PFILE
clause when issuing the STARTUP
command.
See Also:
Migrating to a Server Parameter File
If you are currently using a text initialization parameter file, then you can migrate to a server parameter file.
To migrate to a server parameter file:
Server Parameter File Default Names and Locations
Oracle recommends that you allow the database to give the SPFILE the default name and store it in the default location. This eases administration of your database. For example, the STARTUP
command assumes this default location to read the SPFILE.
The following table shows the default name and location for both the text initialization parameter file (PFILE) and server parameter file (SPFILE) for the UNIX, Linux, and Windows platforms, both with and without the presence of Oracle Automatic Storage Management (Oracle ASM). The table assumes that the SPFILE is a file.
Table 4-1 PFILE and SPFILE Default Names and Locations on UNIX, Linux, and Windows
Platform | PFILE Default Name | SPFILE Default Name | PFILE Default Location | SPFILE Default Location |
---|---|---|---|---|
UNIX and Linux |
|
|
Oracle_Home |
Without Oracle ASM: Oracle_Home When Oracle ASM is present: In the same disk group as the data files (assuming the database was created with DBCA) |
Windows |
|
|
Oracle_Home |
Without Oracle ASM: OH When Oracle ASM is present: In the same disk group as the data files (assuming the database was created with DBCA) |
Note:
Upon startup, the instance first searches for an SPFILE named spfile
ORACLE_SID
.ora
, and if not found, searches for spfile.ora
. Using spfile.ora
enables all Real Application Cluster (Oracle RAC) instances to use the same server parameter file.
If neither SPFILE is found, the instance searches for the text initialization parameter file init
ORACLE_SID
.ora
.
If you create an SPFILE in a location other than the default location, you must create in the default PFILE location a "stub" PFILE that points to the server parameter file. For more information, see "Starting Up a Database".
When you create the database with DBCA when Oracle ASM is present, DBCA places the SPFILE in an Oracle ASM disk group, and also causes this stub PFILE to be created.
Creating a Server Parameter File
You use the CREATE SPFILE
statement to create a server parameter file. You must have the SYSDBA
, SYSOPER
, or SYSBACKUP
administrative privilege to execute this statement.
To create a server parameter file:
-
Run the
CREATE SPFILE
statement.
Note:
When you use the Database Configuration Assistant to create a database, it automatically creates a server parameter file for you.
The CREATE SPFILE
statement can be executed before or after instance startup. However, if the instance has been started using a server parameter file, an error is raised if you attempt to re-create the same server parameter file that is currently being used by the instance.
You can create a server parameter file (SPFILE) from an existing text initialization parameter file or from memory. Creating the SPFILE from memory means copying the current values of initialization parameters in the running instance to the SPFILE.
The following example creates a server parameter file from text initialization parameter file /u01/oracle/dbs/init.ora
. In this example no SPFILE
name is specified, so the file is created with the platform-specific default name and location shown in Table 4-1.
CREATE SPFILE FROM PFILE='/u01/oracle/dbs/init.ora';
The next example illustrates creating a server parameter file and supplying a name and location.
CREATE SPFILE='/u01/oracle/dbs/test_spfile.ora'
FROM PFILE='/u01/oracle/dbs/test_init.ora';
The next example illustrates creating a server parameter file in the default location from the current values of the initialization parameters in memory.
CREATE SPFILE FROM MEMORY;
Whether you use the default SPFILE name and default location or specify an SPFILE name and location, if an SPFILE of the same name already exists in the location, it is overwritten without a warning message.
When you create an SPFILE from a text initialization parameter file, comments specified on the same lines as a parameter setting in the initialization parameter file are maintained in the SPFILE. All other comments are ignored.
The SPFILE Initialization Parameter
The SPFILE
initialization parameter contains the name of the current server parameter file.
When the default server parameter file is used by the database—that is, you issue a STARTUP
command and do not specify a PFILE
parameter—the value of SPFILE
is internally set by the server. The SQL*Plus command SHOW PARAMETERS SPFILE
(or any other method of querying the value of a parameter) displays the name of the server parameter file that is currently in use.
Changing Initialization Parameter Values
You can change initialization parameter values to affect the operation of a database instance.
- About Changing Initialization Parameter Values
TheALTER SYSTEM
statement enables you to set, change, or restore to default the values of initialization parameters. If you are using a text initialization parameter file, theALTER SYSTEM
statement changes the value of a parameter only for the current instance, because there is no mechanism for automatically updating text initialization parameters on disk. You must update them manually to be passed to a future instance. Using a server parameter file overcomes this limitation. - Setting or Changing Initialization Parameter Values
With a server parameter file, use theSET
clause of theALTER SYSTEM
statement to set or change initialization parameter values.
About Changing Initialization Parameter Values
The ALTER SYSTEM
statement enables you to set, change, or restore to default the values of initialization parameters. If you are using a text initialization parameter file, the ALTER SYSTEM
statement changes the value of a parameter only for the current instance, because there is no mechanism for automatically updating text initialization parameters on disk. You must update them manually to be passed to a future instance. Using a server parameter file overcomes this limitation.
There are two kinds of initialization parameters:
-
Dynamic initialization parameters can be changed for the current Oracle Database instance. The changes take effect immediately.
-
Static initialization parameters cannot be changed for the current instance. You must change these parameters in the text initialization file or server parameter file and then restart the database before changes take effect.
Parent topic: Changing Initialization Parameter Values
Setting or Changing Initialization Parameter Values
With a server parameter file, use the SET
clause of the ALTER SYSTEM
statement to set or change initialization parameter values.
-
Run an
ALTER SYSTEM SET
statement.
For example, the following statement changes the maximum number of failed login attempts before the connection is dropped. It includes a comment, and explicitly states that the change is to be made only in the server parameter file.
ALTER SYSTEM SET SEC_MAX_FAILED_LOGIN_ATTEMPTS=3 COMMENT='Reduce from 10 for tighter security.' SCOPE=SPFILE;
The next example sets a complex initialization parameter that takes a list of attributes. Specifically, the parameter value being set is the LOG_ARCHIVE_DEST_n
initialization parameter. This statement could change an existing setting for this parameter or create a new archive destination.
ALTER SYSTEM SET LOG_ARCHIVE_DEST_4='LOCATION=/u02/oracle/rbdb1/',MANDATORY,'REOPEN=2' COMMENT='Add new destination on Nov 29' SCOPE=SPFILE;
When a value consists of a list of parameters, you cannot edit individual attributes by the position or ordinal number. You must specify the complete list of values each time the parameter is updated, and the new list completely replaces the old list.
- The SCOPE Clause in ALTER SYSTEM SET Statements
The optionalSCOPE
clause inALTER SYSTEM SET
statements specifies the scope of an initialization parameter change.
Parent topic: Changing Initialization Parameter Values
The SCOPE Clause in ALTER SYSTEM SET Statements
The optional SCOPE
clause in ALTER SYSTEM SET
statements specifies the scope of an initialization parameter change.
SCOPE Clause | Description |
---|---|
|
The change is applied in the server parameter file only. The effect is as follows:
This is the only |
|
The change is applied in memory only. The effect is as follows:
For static parameters, this specification is not allowed. |
|
The change is applied in both the server parameter file and memory. The effect is as follows:
For static parameters, this specification is not allowed. |
It is an error to specify SCOPE=SPFILE
or SCOPE=BOTH
if the instance did not start up with a server parameter file. The default is SCOPE=BOTH
if a server parameter file was used to start up the instance, and MEMORY
if a text initialization parameter file was used to start up the instance.
For dynamic parameters, you can also specify the DEFERRED
keyword. When specified, the change is effective only for future sessions.
When you specify SCOPE
as SPFILE
or BOTH
, an optional COMMENT
clause lets you associate a text string with the parameter update. The comment is written to the server parameter file.
Parent topic: Setting or Changing Initialization Parameter Values
Clearing Initialization Parameter Values
You can use the ALTER SYSTEM RESET
statement to clear an initialization parameter value. When you do so, the initialization parameter value is changed to its default value or its startup value.
The ALTER SYSTEM RESET
statement includes a SCOPE
clause. When executed in a non-CDB or a multitenant container database (CDB) root, the ALTER SYSTEM RESET
statement and SCOPE
clause behave differently than when the statement is executed in a pluggable database (PDB), an application root, or an application PDB.
The startup value of a parameter is the value of the parameter in memory after the instance's startup or PDB open has completed. This value can be seen in the VALUE
and DISPLAY_VALUE
columns in the V$SYSTEM_PARAMETER
view immediately after startup. The startup value can be different from the value in the spfile or the default value (if the parameter is not set in the spfile), since the value of the parameter can be adjusted internally at startup.
The SCOPE
values for the ALTER SYSTEM RESET
statement behave as follows in a non-CDB and in the CDB$ROOT
of a CDB:
-
SCOPE=SPFILE
: If an instance is using spfile, removes the parameter from the spfile; the default value takes effect upon the next instance startup. -
SCOPE=MEMORY
: The startup value takes effect immediately. However, the change is not stored in instance's spfile and will be lost upon instance restart. -
SCOPE=BOTH
: If an instance is using spfile, removes the parameter from the spfile; the default value takes effect immediately and the change is available across instance restart.
Note:
SCOPE=BOTH
changes the way SCOPE=MEMORY
behaves. After SCOPE=BOTH
is issued, SCOPE=MEMORY
always resets the parameter to the default value.
The SCOPE
values for the ALTER SYSTEM RESET
statement behave as follows in a PDB, an application root, or an application PDB:
-
SCOPE=SPFILE
: Removes the parameter from the container's spfile; the container will inherit the parameter value from its root upon the next PDB open. -
SCOPE=MEMORY
: There are two cases:-
The parameter is present in container's spfile when the container is opened. The parameter value is updated to the startup value for the parameter. This change is not stored in container’s spfile and will be lost upon the next container open.
-
The parameter is not present in container’s spfile when the container is opened. The container starts inheriting the parameter value from its root.
-
-
SCOPE=BOTH
: Removes the parameter from the container’s spfile; the container will inherit the parameter value from its root.
Note:
-
SCOPE=BOTH
changes the waySCOPE=MEMORY
behaves. AfterSCOPE=BOTH
is issued, the container always inherits the parameter value from its root whenSCOPE=MEMORY
is issued. -
In a case where a container inherits a parameter value from its root, a PDB inherits the value from
CDB$ROOT
. In an application container, an application PDB inherits the parameter value from its application root, and an application root inherits the parameter value fromCDB$ROOT
.
See Also:
Oracle Database SQL Language Reference for information about the ALTER SYSTEM
command
Exporting the Server Parameter File
You can use the CREATE PFILE
statement to export a server parameter file (SPFILE) to a text initialization parameter file.
-
Run a
CREATE PFILE
statement.
Exporting the server parameter file might be necessary for several reasons:
-
For diagnostic purposes, listing all of the parameter values currently used by an instance. This is analogous to the SQL*Plus
SHOW PARAMETERS
command or selecting from theV$PARAMETER
orV$PARAMETER2
views. -
To modify the server parameter file by first exporting it, editing the resulting text file, and then re-creating it using the
CREATE SPFILE
statement
The exported file can also be used to start up an instance using the PFILE
clause.
You must have the SYSDBA
, SYSOPER
, or SYSBACKUP
administrative privilege to execute the CREATE PFILE
statement. The exported file is created on the database server system. It contains any comments associated with the parameter in the same line as the parameter setting.
The following example creates a text initialization parameter file from the SPFILE:
CREATE PFILE FROM SPFILE;
Because no names were specified for the files, the database creates an initialization parameter file with a platform-specific name, and it is created from the platform-specific default server parameter file.
The following example creates a text initialization parameter file from a server parameter file, but in this example the names of the files are specified:
CREATE PFILE='/u01/oracle/dbs/test_init.ora' FROM SPFILE='/u01/oracle/dbs/test_spfile.ora';
Note:
An alternative is to create a PFILE from the current values of the initialization parameters in memory. The following is an example of the required command:
CREATE PFILE='/u01/oracle/dbs/test_init.ora' FROM MEMORY;
Backing Up the Server Parameter File
You can create a backup of your server parameter file (SPFILE) by exporting it. If the backup and recovery strategy for your database is implemented using Recovery Manager (RMAN), then you can use RMAN to create a backup of the SPFILE. The SPFILE is backed up automatically by RMAN when you back up your database, but RMAN also enables you to specifically create a backup of the currently active SPFILE.
-
Back up the server parameter file either by exporting it or by using RMAN.
Recovering a Lost or Damaged Server Parameter File
You can recover the server parameter file (SPFILE). If your server parameter file (SPFILE) becomes lost or corrupted, then the current instance may fail, or the next attempt at starting the database instance may fail.
There are several ways to recover the SPFILE:
-
If the instance is running, issue the following command to re-create the SPFILE from the current values of initialization parameters in memory:
CREATE SPFILE FROM MEMORY;
This command creates the SPFILE with the default name and in the default location. You can also create the SPFILE with a new name or in a specified location. See "Creating a Server Parameter File" for examples.
-
If you have a valid text initialization parameter file (PFILE), re-create the SPFILE from the PFILE with the following statement:
CREATE SPFILE FROM PFILE;
This command assumes that the PFILE is in the default location and has the default name. See "Creating a Server Parameter File" for the command syntax to use when the PFILE is not in the default location or has a nondefault name.
-
Restore the SPFILE from backup.
See "Backing Up the Server Parameter File" for more information.
-
If none of the previous methods are possible in your situation, perform these steps:
-
Create a text initialization parameter file (PFILE) from the parameter value listings in the alert log.
When an instance starts up, the initialization parameters used for startup are written to the alert log. You can copy and paste this section from the text version of the alert log (without XML tags) into a new PFILE.
See Oracle Database Administrator’s Guide for more information.
-
Create the SPFILE from the PFILE.
See "Creating a Server Parameter File" for instructions.
-
Read/Write Errors During a Parameter Update
If an error occurs while reading or writing the server parameter file during a parameter update, the error is reported in the alert log and all subsequent parameter updates to the server parameter file are ignored. At this point, you can take one of the following actions:
-
Shut down the instance, recover the server parameter file and described earlier in this section, and then restart the instance.
-
Continue to run the database if you do not care that subsequent parameter updates will not be persistent.
Methods for Viewing Parameter Settings
You can view parameter settings using several different methods.
Method | Description |
---|---|
|
This SQL*Plus command displays the values of initialization parameters in effect for the current session. |
|
This SQL*Plus command displays the values of initialization parameters in the server parameter file (SPFILE). |
|
This SQL statement creates a text initialization parameter file (PFILE) from the SPFILE or from the current in-memory settings. You can then view the PFILE with any text editor. |
|
This view displays the values of initialization parameters in effect for the current session. |
|
This view displays the values of initialization parameters in effect for the current session. It is easier to distinguish list parameter values in this view because each list parameter value appears in a separate row. |
|
This view displays the values of initialization parameters in effect for the instance. A new session inherits parameter values from the instance-wide values. |
|
This view displays the values of initialization parameters in effect for the instance. A new session inherits parameter values from the instance-wide values. It is easier to distinguish list parameter values in this view because each list parameter value appears in a separate row. |
|
This view displays the current contents of the SPFILE. The view returns |
See Also:
Oracle Database Reference for a complete description of views
Managing Application Workloads with Database Services
A database service is a named representation of one or more database instances. Services enable you to group database workloads and route a particular work request to an appropriate instance.
- Database Services
A database service represents a single database. This database can be a single-instance database or an Oracle Real Application Clusters (Oracle RAC) database with multiple concurrent database instances. A global database service is a service provided by multiple databases synchronized through data replication. - Global Data Services
Starting with Oracle Database 12c, you can use Global Data Services (GDS) for workload management involving multiple Oracle databases. - Database Service Data Dictionary Views
You can query data dictionary views to find information about database services.
Parent topic: Creating a CDB: Advanced Topics
Database Services
A database service represents a single database. This database can be a single-instance database or an Oracle Real Application Clusters (Oracle RAC) database with multiple concurrent database instances. A global database service is a service provided by multiple databases synchronized through data replication.
- About Database Services
Database services divide workloads for a single database into mutually disjoint groupings. - Database Services and Performance
Database services offer an extra dimension in performance tuning. - Oracle Database Features That Use Database Services
Several Oracle Database features support database services. - Creating Database Services
There are a few ways to create database services, depending on your database configuration.
Parent topic: Managing Application Workloads with Database Services
About Database Services
Database services divide workloads for a single database into mutually disjoint groupings.
Each database service represents a workload with common attributes, service-level thresholds, and priorities. The grouping is based on attributes of work that might include the application function to be used, the priority of execution for the application function, the job class to be managed, or the data range used in the application function or job class. For example, the Oracle E-Business Suite defines a database service for each responsibility, such as general ledger, accounts receivable, order entry, and so on. When you configure database services, you give each service a unique name, associated performance goals, and associated importance. The database services are tightly integrated with Oracle Database and are maintained in the data dictionary.
Connection requests can include a database service name. Thus, middle-tier applications and client/server applications use a service by specifying the database service as part of the connection in TNS connect data. If no database service name is included and the Net Services file listener.ora designates a default database service, then the connection uses the default database service.
Database services enable you to configure a workload for a single database, administer it, enable and disable it, and measure the workload as a single entity. You can do this using standard tools such as the Database Configuration Assistant (DBCA), Oracle Net Configuration Assistant, and Oracle Enterprise Manager Cloud Control (Cloud Control). Cloud Control supports viewing and operating services as a whole, with drill down to the instance-level when needed.
In an Oracle Real Application Clusters (Oracle RAC) environment, a database service can span one or more instances and facilitate workload balancing based on transaction performance. This capability provides end-to-end unattended recovery, rolling changes by workload, and full location transparency. Oracle RAC also enables you to manage several database service features with Cloud Control, the DBCA, and the Server Control utility (SRVCTL
).
Database services describe applications, application functions, and data ranges as either functional services or data-dependent services. Functional services are the most common mapping of workloads. Sessions using a particular function are grouped together. In contrast, data-dependent routing routes sessions to database services based on data keys. The mapping of work requests to database services occurs in the object relational mapping layer for application servers and TP monitors. For example, in Oracle RAC, these ranges can be completely dynamic and based on demand because the database is shared.
In addition to database services that are used by applications, Oracle Database also supports two internal database services: SYS$BACKGROUND
is used by the background processes only, and SYS$USERS
is the default database service for user sessions that are not associated with services.
Using database services requires no changes to your application code. Client-side work can connect to a named database service. Server-side work, such as Oracle Scheduler, parallel execution, and Oracle Database Advanced Queuing, set the database service name as part of the workload definition. Work requests executing under a database service inherit the performance thresholds for the service and are measured as part of the service.
See Also:
-
Oracle Real Application Clusters Administration and Deployment Guide for information about using services in an Oracle RAC environment
-
Oracle Database Net Services Administrator's Guide for information on connecting to a service
-
The Cloud Control online help
Parent topic: Database Services
Database Services and Performance
Database services offer an extra dimension in performance tuning.
Tuning by "service and SQL" can replace tuning by "session and SQL" in the majority of systems where all sessions are anonymous and shared. With database services, workloads are visible and measurable. Resource consumption and waits are attributable by application. Additionally, resources assigned to database services can be augmented when loads increase or decrease. This dynamic resource allocation enables a cost-effective solution for meeting demands as they occur. For example, database services are measured automatically, and the performance is compared to service-level thresholds. Performance violations are reported to Cloud Control, enabling the execution of automatic or scheduled solutions.
Parent topic: Database Services
Oracle Database Features That Use Database Services
Several Oracle Database features support database services.
The Automatic Workload Repository (AWR) manages the performance of services. AWR records database service performance, including execution times, wait classes, and resources consumed by services. AWR alerts warn when database service response time thresholds are exceeded. The dynamic views report current service performance metrics with one hour of history. Each database service has quality-of-service thresholds for response time and CPU consumption.
In addition, the Database Resource Manager can map database services to consumer groups. Therefore, you can automatically manage the priority of one database service relative to others. You can use consumer groups to define relative priority in terms of either ratios or resource consumption.
You also can specify an edition attribute for a database service. Editions make it possible to have two or more versions of the same objects in the database. When you specify an edition attribute for a database service, all subsequent connections that specify the database service use this edition as the initial session edition.
Specifying an edition as a database service attribute can make it easier to manage resource usage. For example, database services associated with an edition can be placed on a separate instance in an Oracle RAC environment, and the Database Resource Manager can manage resources used by different editions by associating resource plans with the corresponding database services.
For Oracle Scheduler, you optionally assign a database service when you create a job class. During execution, jobs are assigned to job classes, and job classes can run within database services. Using database services with job classes ensures that the work executed by the job scheduler is identified for workload management and performance tuning.
For parallel query and parallel DML, the query coordinator connects to a database service just like any other client. The parallel query processes inherit the database service for the duration of the execution. At the end of query execution, the parallel execution processes revert to the default database service.
See Also:
Oracle Database Administrator’s Guide to learn about the following topics:
Parent topic: Database Services
Creating Database Services
There are a few ways to create database services, depending on your database configuration.
Note:
Starting with Oracle Database 19c, customer use of the
SERVICE_NAMES
parameter is deprecated. It can be
desupported in a future release. To manage your services, Oracle recommends that
you use the SRVCTL
or GDSCTL
command line
utilities, or the DBMS_SERVICE
package.
Note:
This section describes creating services locally.
To create a database service:
-
If your single-instance database is being managed by Oracle Restart, use the
SRVCTL
utility to create the database service.srvctl add service -db db_unique_name -service service_name
-
If your single-instance database is not being managed by Oracle Restart, do one of the following:
-
Append the desired database service name to the
SERVICE_NAMES
parameter. -
Call the
DBMS_SERVICE.CREATE_SERVICE
package procedure.
-
-
(Optional) Define database service attributes with Cloud Control or with
DBMS_SERVICE.MODIFY_SERVICE
.
Oracle Net Listener (the listener) receives incoming client connection requests and manages the traffic of these requests to the database server. The listener handles connections for registered services, and it supports dynamic service registration.
See Also:
-
Oracle Database Administrator’s Guide for information about Oracle Restart
-
Oracle Database PL/SQL Packages and Types Reference for information about the
DBMS_SERVICE
package -
Oracle Real Application Clusters Administration and Deployment Guide for information about creating a service in an Oracle RAC environment
-
Oracle Database Net Services Administrator's Guide for more information about Oracle Net Listener and services
Parent topic: Database Services
Global Data Services
Starting with Oracle Database 12c, you can use Global Data Services (GDS) for workload management involving multiple Oracle databases.
GDS enables administrators to automatically and transparently manage client workloads across replicated databases that offer common services. These common services are known as global services.
GDS enables you to integrate multiple databases in various locations into private GDS configurations that can be shared by global clients. Benefits include the following:
-
Enables central management of global resources
-
Provides global scalability, availability, and run-time load balancing
-
Allows you to dynamically add databases to the GDS configuration and dynamically migrate global services
-
Extends service management, load balancing, and failover capabilities for distributed environments of replicated databases that use features such as Oracle Active Data Guard, Oracle GoldenGate, and so on
-
Provides high availability through seamless failover of global services across databases (located both locally or globally)
-
Provides workload balancing both within and between data centers through services, connection load balancing, and runtime load balancing
-
Allows efficient utilization of the resources of the GDS configuration to service client requests
See Also:
Oracle Database Global Data Services Concepts and Administration Guide for an overview of Global Data Services
Parent topic: Managing Application Workloads with Database Services
Database Service Data Dictionary Views
You can query data dictionary views to find information about database services.
You can find information about database services in the following views:
The following additional views also contain some information about database services:
The ALL_SERVICES
view includes a GLOBAL_SERVICE
column, and the V$SERVICES
and V$ACTIVE_SERVICES
views contain a GLOBAL
column. These views and columns enable you to determine whether a database service is a global service.
Parent topic: Managing Application Workloads with Database Services
Managing Standard Edition High Availability for Oracle Databases
The Standard Edition High Availability feature provides protection against unplanned outages for Oracle Database Standard Edition 2 single instance databases using Oracle Clusterware.
Note:
Standard Edition High Availability is supported in this release of Oracle Database.Note:
Thesrvctl
commands
used with Standard Edition High Availability are different from those used with Oracle
Restart. For Standard Edition High Availability, refer to the srvctl
commands documented in the Oracle Real Application Clusters Administration and
Deployment Guide.
- About Standard Edition High Availability
In this release, you can install Oracle Database Standard Edition 2 in high availability mode. - Requirements for Using Standard Edition High Availability With Oracle Databases
To use Standard Edition High Availability, deploy Oracle Database Standard Edition 2 in accordance with these configuration requirements. - Enabling Standard Edition High Availability for Oracle Databases
You enable Standard Edition High Availability to provide cluster-based failover for an Oracle Database Standard Edition 2 database. - Relocating a Standard Edition High Availability Database to Another Node
To manage planned outages, you can relocate an Oracle Database Standard Edition 2 database that uses Standard Edition High Availability to another configured node. - Adding a Node to a Standard Edition High Availability Database
Adding new nodes to an existing Standard Edition High Availability configuration provides enhanced failover capabilities to your Standard Edition 2 database. - Removing a Configured Node from a Standard Edition High Availability Database
Usesrvctl
commands to remove a node from the list of nodes configured for a Standard Edition High Availability database. - Starting and Stopping Standard Edition High Availability Databases
Usesrvctl
commands to start or stop an Oracle Database that is configured for Standard Edition High Availability. - Deactivating Standard Edition High Availability for Oracle Databases
When you deactivate Standard Edition High Availability for a single instance Oracle Database, the database is no longer part of a high availability failover configuration.
Related Topics
Parent topic: Creating a CDB: Advanced Topics
About Standard Edition High Availability
In this release, you can install Oracle Database Standard Edition 2 in high availability mode.
Standard Edition High Availability provides cluster-based failover for single-instance Standard Edition Oracle Databases using Oracle Clusterware.
Oracle Standard Edition High Availability benefits from the cluster capabilities and storage solutions that are already part of Oracle Grid Infrastructure, such as Oracle Clusterware, Oracle Automatic Storage Management (Oracle ASM) and Oracle Advanced Cluster File System (Oracle ACFS).
Using integrated, shared, and concurrently mounted storage, such as Oracle ASM and Oracle ACFS for database files as well as for unstructured data, enables Oracle Grid Infrastructure to restart an Oracle Database on a failover node much faster than any cluster solution that relies on failing over and remounting volumes and file systems.
Standard Edition High Availability is supported on Linux x86-64, Microsoft Windows, and HP-UX Itanium.
Note:
This section is specific to Standard Edition High Availability, which provides cluster-based database failover for Standard Edition Oracle Databases 21c and later. For more information about high availability options for Oracle Database, see Oracle Clusterware Administration and Deployment Guide.Requirements for Using Standard Edition High Availability With Oracle Databases
To use Standard Edition High Availability, deploy Oracle Database Standard Edition 2 in accordance with these configuration requirements.
- The database is created in a cluster running Oracle Grid Infrastructure for a Standalone Cluster, with its database files placed in Oracle Automatic Storage Management (Oracle ASM) or Oracle Advanced Cluster File System (Oracle ACFS).
- When using the Database Configuration Assistant, do not create a listener when creating an Oracle Database Standard Edition 2 database that you want to configure for Standard Edition High Availability.
- Register the database with Single Client Access Name (SCAN) listeners as remote listeners, and node listeners as the local listener.
- Create a database service. Use this service, instead of the default database service, when you connect applications or database clients to the database.
- Ensure that the server parameter file (
spfile
) and password file are on Oracle ASM or Oracle ACFS. If thespfile
and password file were placed on a local file system when the database was created or configured, then move these files to Oracle ASM or Oracle ACFS.
Refer to the database installation documentation for additional requirements that must be met.
Related Topics
Enabling Standard Edition High Availability for Oracle Databases
You enable Standard Edition High Availability to provide cluster-based failover for an Oracle Database Standard Edition 2 database.
Note:
The steps in this topic must be performed after you install the Oracle Database software binaries to configure Standard Edition High Availability, as described in the Oracle Database Installation Guide for Linux, and create a database. If you have an existing Standard Edition 2 database that runs on one cluster node, and you want to enable Standard Edition High Availability for this database, you need to add a node to the configuration.Prerequisites
-
Ensure that the initialization parameter
local_listener
is not set. This is to enable node listeners to be automatically used and database connections to be made over the node virtual IP address.Use the following command to display the current listener configuration:
SQL> SHOW PARAMETER LOCAL_LISTENER;
If the output of the above command shows a local listener name, then reset the local listener using the following command:
SQL> ALTER SYSTEM RESET LOCAL_LISTENER SCOPE = BOTH;
The database must be restarted for the listener configuration change to take effect. However, if the database is relocated to another node, as part of verifying the Standard Edition High Availability configuration, then the database need not be restarted.
-
When the database files are stored in Oracle Advanced Cluster File System (Oracle ACFS), the Oracle ACFS file system must be registered in Oracle Clusterware and the dependency of the database resource on the corresponding Oracle ACFS resources must be configured using
srvctl
commands. For example:$ srvctl modify database -db se2cdb2 -acfspath /u01/app/oradata
To enable Standard Edition High Availability for an Oracle Database Standard Edition 2 database:
After you enable Standard Edition High Availability for a database:
- When there is an unplanned outage of the node which runs the database instance, the instance is restarted on an available node in the configured node list.
- When there is an unplanned termination of the database instance, an attempt is made to restart the instance on the current node. If the restart fails, a failover is initiated to an available node in the configured node list.
- When the node which runs the database instance completely loses connectivity to the public network, the instance is relocated to an available node in the configured node list.
Note:
The order of nodes in the node list determines the node on which the database is started. Oracle Clusterware attempts to start the database on the first node in the node list. If the first node is unavailable, it moves to the next node in the node list.
Oracle Clusterware also uses the order of nodes in the node list to determine the failover target, if the current node fails. Failover targets are considered starting with the first node in the list and until a suitable candidate is found and unless other circumstances in the cluster prevent this order to determine the failover node.
To verify the Standard Edition High Availability configuration,
especially its current configured node list, use the srvctl config
database
command. For example:
$ srvctl config database -db se2cdb
...
Type: SINGLE
...
Configured nodes:
node3, node5
Notice from the output that the type of database is single, but there are multiple configured nodes. This indicates that Standard Edition High Availability is enabled.
Further verification can be performed by relocating the database to another configured node.
Relocating a Standard Edition High Availability Database to Another Node
To manage planned outages, you can relocate an Oracle Database Standard Edition 2 database that uses Standard Edition High Availability to another configured node.
The node to which the database is being relocated must be part of the configured node list for this database.
To relocate an active Oracle Database Standard Edition 2 database from its current node to another configured node:
-
Use the
srvctl relocate
command.This command performs an offline relocation. It shuts down the database on the existing node and then starts it on the new node.
For example, the following command relocates the Standard Edition 2
database named se2cdb
, that uses Standard Edition High
Availability, to the node node5
:
$ srvctl relocate database -db se2cdb -node node5
Note:
The–abort
and
–revert
options of srvctl relocate database
command are not supported with Standard Edition High Availability.
Adding a Node to a Standard Edition High Availability Database
Adding new nodes to an existing Standard Edition High Availability configuration provides enhanced failover capabilities to your Standard Edition 2 database.
To add a node to a Standard Edition High Availability database:
Removing a Configured Node from a Standard Edition High Availability Database
Use srvctl
commands to remove a node from the list of nodes
configured for a Standard Edition High Availability database.
oracle
). On Windows, log in to
the database host computer as Administrator.
To remove a configured node from a database that uses Standard Edition High Availability:
Example 4-1 Removing a Configured Node from a Standard Edition High Availability Database
The example assumes that the database with unique name
sec2cdb
uses Standard Edition High Availability and the
configured nodes are node1
, node2
, and
node3
. The database is currently running on
node3
. To remove node2
from the list of
configured nodes for this database, log in as a user who installed the Oracle
Database home and run the following command:
$ srvctl modify database -db sec2cdb -node node1,node3
Starting and Stopping Standard Edition High Availability Databases
Use srvctl
commands to start or stop an Oracle Database
that is configured for Standard Edition High Availability.
Navigate to the Oracle Database home directory. On Linux, log in to the
database host computer as the Oracle installation owner user account
(oracle
). On Windows, log in to the database host computer as
Administrator.
To start up a Standard Edition High Availability database:
-
Use the
srvctl start database
command.Optionally, include the
-node
argument to specify the node on which the database must be started.
To stop a Standard Edition High Availability database:
- Use the
srvctl stop database
command
Example 4-2 Starting Up a Standard Edition High Availability Database on a Specified Node
This example starts up a database with the unique name
se2cdb
on the node named node3
.
$ srvctl start database -db sec2cdb -node node3
Example 4-3 Stopping a Standard Edition High Availability Database
This example stops a database instance that is configured to use Standard
Edition High Availability. The unique name of the database is
sec2cdb
.
$ srvctl stop database -db sec2cdb
Deactivating Standard Edition High Availability for Oracle Databases
When you deactivate Standard Edition High Availability for a single instance Oracle Database, the database is no longer part of a high availability failover configuration.
To deactivate Standard Edition High Availability for an Oracle Database:
-
Use the
srvctl modify
command and include only one node in the-node
argument.
Example 4-4 Deactivating the Use of Standard Edition High Availability for an Oracle Database
This example deactivates the use of Standard Edition High Availability
for the database with unique name se2cdb
and configures only one
node, node1
, for this database:
srvctl modify database -db se2cdb -node node1
All previously configured nodes are removed and the database is now a single-instance database that is registered with Oracle Clusterware.
Cloning a Database
This section describes various methods of cloning an Oracle database.
- Cloning a Database in a Multitenant Environment
You can clone a database in a multitenant environment. - Cloning a Database with Oracle Automatic Storage Management (Oracle ASM)
Oracle Automatic Storage Management (Oracle ASM) provides support for cloning a pluggable database (PDB) in a multitenant container database (CDB). Oracle ASM does not support cloning a non-CDB.
Parent topic: Creating a CDB: Advanced Topics
Cloning a Database in a Multitenant Environment
You can clone a database in a multitenant environment.
Refer to Oracle Multitenant Administrator's Guide for more information about cloning a database in a multitenant environment.
Parent topic: Cloning a Database
Cloning a Database with Oracle Automatic Storage Management (Oracle ASM)
Oracle Automatic Storage Management (Oracle ASM) provides support for cloning a pluggable database (PDB) in a multitenant container database (CDB). Oracle ASM does not support cloning a non-CDB.
See the following guides for more information:
Parent topic: Cloning a Database
Configuring EM Express for a CDB
For a CDB, you can configure Oracle Enterprise Manager Database Express (EM Express) for the root and for each PDB by setting a global HTTPS port, or you can set a different port for every container in the CDB.
Note:
EM Express is a web-based database management tool that is built inside the Oracle Database. It supports key performance management and basic database administration functions. Many of EM Express's capabilities are also available in Oracle SQL Developer, which is included in all Oracle Database editions. Oracle recommends that you replace your use of EM Express with Oracle SQL Developer.
To configure EM Express for a CDB:
You can set a global port, which enables you to use EM Express to connect to all PDBs in the CDB using the HTTPS port for the CDB. Alternatively, you can set a different HTTPS port for every container in a CDB.
-
In SQL*Plus, access a container in a CDB.
The user must have common
SYSDBA
administrative privilege, and you must exercise this privilege usingAS SYSDBA
at connect time. The container can be the root or a PDB. -
Set the port in one of the following ways:
-
To set the global port, connect to the
CDB$ROOT
, and issue the following SQL statement to configure the global port for the CDB:EXEC DBMS_XDB_CONFIG.SETGLOBALPORTENABLED(TRUE);
-
To set the HTTPS port for the current container, run the following procedure:
exec DBMS_XDB_CONFIG.SETHTTPSPORT(https_port_number);
Replace
https_port_number
with the appropriate HTTPS port number.
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Access EM Express in one of the following ways:
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To use the global port, enter the EM Express URL provided by Database Configuration Assistant (DBCA) when it configured the CDB that includes the PDB. When the EM Express login screen appears, specify your administrator credentials, and enter the name of the PDB that you want to connect to in the Container Name field.
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The URL for the HTTPS port for a container:
https://database_hostname:https_port_number/em/
Replace
database_hostname
with the host name of the computer on which the database instance is running, and replacehttps_port_number
with the appropriate HTTPS port number.
When connected to the root, EM Express displays data and enables actions that apply to the entire CDB. When connected to a PDB, EM Express displays data and enables actions that apply to the PDB only.
Note:
If the listener is not configured on port 1521, then you must manually configure the port for EM Express.
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Parent topic: Creating a CDB: Advanced Topics
Dropping a Database
Dropping a CDB involves removing its data files, online redo logs, control files, and initialization parameter files.
WARNING:
Dropping a CDB deletes all its data.
To drop a database:
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Submit the following statement:
DROP DATABASE;
The DROP DATABASE
statement first deletes all control files and all other database files listed in the control file. It then shuts down the database instance.
To use the DROP DATABASE
statement successfully, the database must be mounted in exclusive and restricted mode.
The DROP DATABASE
statement has no effect on archived redo log files, nor does it have any effect on copies or backups of the database. It is best to use RMAN to delete such files.
If you used the Database Configuration Assistant to create your database, you can use that tool to delete (drop) your database and remove the files.
See Also:
Parent topic: Creating a CDB: Advanced Topics