|Oracle® Database Administrator's Guide
10g Release 1 (10.1)
Part Number B10739-01
Use the Database Configuration Assistant (DBCA).
DBCA can be launched by the Oracle Universal Installer, depending upon the type of install that you select, and provides a graphical user interface (GUI) that guides you through the creation of a database. You can also launch DBCA as a standalone tool at any time after Oracle Database installation to create or make a copy (clone) of a database. Please refer to Oracle Database 2 Day DBA for details information on creating a database using DBCA.
You can use the
CREATE DATABASE SQL statement to create a database. If you do so, you must complete additional actions before you have an operational database. These actions include creating users and temporary tablespaces, building views of the data dictionary tables, and installing Oracle built-in packages. These actions can be performed by executing prepared scripts, many of which are supplied for you.
If you have existing scripts for creating your database, consider editing those scripts to take advantage of new Oracle Database features. Oracle provides a sample database creation script and a sample initialization parameter file with the Oracle Database software files. Both the script and the file can be edited to suit your needs. See "Manually Creating an Oracle Database".
Upgrade an existing database.
If you are already using a earlier release of Oracle Database, database creation is required only if you want an entirely new database. You can upgrade your existing Oracle Database and use it with the new release of the database software. The Oracle Database Upgrade Guide manual contains information about upgrading an existing Oracle Database.
The remainder of this chapter discusses creating a database manually.
This section takes you through the planning stage and the actual creation of the database.
Database creation prepares several operating system files to work together as an Oracle Database. You need only create a database once, regardless of how many datafiles it has or how many instances access it. You can create a database to erase information in an existing database and create a new database with the same name and physical structure.
The following topics can help prepare you for database creation.
Prepare to create the database by research and careful planning. Table 2-1 lists some recommended actions:
|Plan the database tables and indexes and estimate the amount of space they will require.||Part II, " Oracle Database Structure and Storage "
|Plan the layout of the underlying operating system files your database will comprise. Proper distribution of files can improve database performance dramatically by distributing the I/O during file access. You can distribute I/O in several ways when you install Oracle software and create your database. For example, you can place redo log files on separate disks or use striping. You can situate datafiles to reduce contention. And you can control data density (number of rows to a data block).||Oracle Database Performance Tuning Guide
Your Oracle operating system specific documentation
|Consider using Oracle-managed files and Automatic Storage Management to create and manage the operating system files that make up your database storage.||Part III, " Automated File and Storage Management "|
|Select the global database name, which is the name and location of the database within the network structure. Create the global database name by setting both the
||"Determining the Global Database Name"|
|Familiarize yourself with the initialization parameters will be contained in the initialization parameter file. Become familiar with the concept and operation of a server parameter file. A server parameter file lets you store and manage your initialization parameters persistently in a server-side disk file.||"Initialization Parameters and Database Creation"
|Select the database character set.
All character data, including data in the data dictionary, is stored in the database character set. You must specify the database character set when you create the database.
If clients using different character sets will access the database, then choose a superset that includes all client character sets. Otherwise, character conversions may be necessary at the cost of increased overhead and potential data loss.
You can also specify an alternate character set.
|Oracle Database Globalization Support Guide|
|Consider what time zones your database must support.
Oracle Database uses one of two time zone files, located in the Oracle home directory, as the source of valid time zones. If you need to use a time zone that is not in the default time zone file (
|"Specifying the Database Time Zone File"|
|Select the standard database block size. This is specified at database creation by the
|"Specifying Database Block Sizes"|
|Determine the appropriate initial sizing for the
||"Creating the SYSAUX Tablespace"|
|Plan to use a default tablespace for non-
||"Creating a Default Permanent Tablespace"|
|Plan to use an undo tablespace, rather than rollback segments, to manage your undo data.||Chapter 10, " Managing the Undo Tablespace"|
|Develop a backup and recovery strategy to protect the database from failure. It is important to protect the control file by multiplexing, to choose the appropriate backup mode, and to manage the online and archived redo logs.||Chapter 6, " Managing the Redo Log"
|Familiarize yourself with the principles and options of starting up and shutting down an instance and mounting and opening a database.||Chapter 3, " Starting Up and Shutting Down "|
Before you can create a new database, the following prerequisites must be met:
The desired Oracle software must be installed. This includes setting various environment variables unique to your operating system and establishing the directory structure for software and database files.
You must have the operating system privileges associated with a fully operational database administrator. You must be specially authenticated by your operating system or through a password file, allowing you to start up and shut down an instance before the database is created or opened. This authentication is discussed in "Database Administrator Authentication".
Sufficient memory must be available to start the Oracle Database instance.
Sufficient disk storage space must be available for the planned database on the computer that runs Oracle Database.
All of these are discussed in the Oracle Database installation guide specific to your operating system. If you use the Oracle Universal Installer, it will guide you through your installation and provide help in setting environment variables and establishing directory structure and authorizations.
This section presents the steps involved when you create a database manually. These steps should be followed in the order presented. The prerequisites described in the preceding section must already have been completed. That is, you have established the environment for creating your Oracle Database, including most operating system dependent environmental variables, as part of the Oracle software installation process.
The examples shown in these steps create an example database
An instance is made up of the system global area (SGA) and the background processes of an Oracle Database. Decide on a unique Oracle system identifier (SID) for your instance and set the
ORACLE_SID environment variable accordingly. This identifier is used to distinguish this instance from other Oracle Database instances that you may create later and run concurrently on your system.
The following example sets the SID for the instance and database we are about to create:
% setenv ORACLE_SID mynewdb
The value of the
DB_NAME initialization parameter should match the SID setting.
You must be authenticated and granted appropriate system privileges in order to create a database. You can use the password file or operating system authentication method. Database administrator authentication and authorization is discussed in the following sections of this book:
The instance for any Oracle Database is started using an initialization parameter file. One way to create the initialization parameter file is to edit a copy of the sample initialization parameter file that Oracle provides on the distribution media, or the sample presented in this book.
For convenience, store your initialization parameter file in the Oracle Database default location, using the default name. Then when you start your database, it will not be necessary to specify the
PFILE parameter of the
STARTUP command, because Oracle Database automatically looks in the default location for the initialization parameter file.
Default initialization parameter file locations are shown in the following table:
|Platform||Default Name||Default Location|
For example, the initialization parameter file for the
For example, the initialization parameter file for the
The following is the initialization parameter file used to create the
mynewdb database on a UNIX system.
control_files = (/u0d/lcg03/control.001.dbf, /u0d/lcg03/control.002.dbf, /u0d/lcg03/control.003.dbf) db_name = lcg03 db_domain = us.oracle.com log_archive_dest_1 = "LOCATION=/net/fstlcg03/private/yaliu/testlog/log.lcg03.fstlcg03/lcg03/arch" log_archive_dest_state_1 = enable db_block_size = 8192 pga_aggregate_target = 2500M processes = 1000 sessions = 1200 open_cursors = 1024 undo_management = AUTO shared_servers = 3 remote_listener = tnsfstlcg03 undo_tablespace = smu_nd1 compatible = 10.1.0.0.0 sga_target = 1500M nls_language = AMERICAN nls_territory = AMERICA db_recovery_file_dest = /net/fstlcg03/private/yaliu/testlog/log.lcg03.fstlcg03/lcg03/arch db_recovery_file_dest_size = 100G
Start SQL*Plus and connect to your Oracle Database instance
$ SQLPLUS /nolog CONNECT SYS/password AS SYSDBA
Oracle recommends that you create a server parameter file as a dynamic means of maintaining initialization parameters. The server parameter file is discussed in "Managing Initialization Parameters Using a Server Parameter File".
The following script creates a server parameter file from the text initialization parameter file and writes it to the default location. The script can be executed before or after instance startup, but after you connect as
SYSDBA. The database must be restarted before the server parameter file takes effect.
-- create the server parameter file CREATE SPFILE='/u01/oracle/dbs/spfilemynewdb.ora' FROM PFILE='/u01/oracle/admin/initmynewdb/scripts/init.ora'; SHUTDOWN -- the next startup will use the server parameter file EXIT
Start an instance without mounting a database. Typically, you do this only during database creation or while performing maintenance on the database. Use the
STARTUP command with the
NOMOUNT clause. In this example, because the server parameter file is stored in the default location, you are not required to specify the
At this point, the SGA is created and background processes are started in preparation for the creation of a new database. The database itself does not yet exist.
CREATE DATABASE mynewdb USER SYS IDENTIFIED BY pz6r58 USER SYSTEM IDENTIFIED BY y1tz5p LOGFILE GROUP 1 ('/u01/oracle/oradata/mynewdb/redo01.log') SIZE 100M, GROUP 2 ('/u01/oracle/oradata/mynewdb/redo02.log') SIZE 100M, GROUP 3 ('/u01/oracle/oradata/mynewdb/redo03.log') SIZE 100M MAXLOGFILES 5 MAXLOGMEMBERS 5 MAXLOGHISTORY 1 MAXDATAFILES 100 MAXINSTANCES 1 CHARACTER SET US7ASCII NATIONAL CHARACTER SET AL16UTF16 DATAFILE '/u01/oracle/oradata/mynewdb/system01.dbf' SIZE 325M REUSE EXTENT MANAGEMENT LOCAL SYSAUX DATAFILE '/u01/oracle/oradata/mynewdb/sysaux01.dbf' SIZE 325M REUSE DEFAULT TABLESPACE tbs_1 DEFAULT TEMPORARY TABLESPACE tempts1 TEMPFILE '/u01/oracle/oradata/mynewdb/temp01.dbf' SIZE 20M REUSE UNDO TABLESPACE undotbs DATAFILE '/u01/oracle/oradata/mynewdb/undotbs01.dbf' SIZE 200M REUSE AUTOEXTEND ON MAXSIZE UNLIMITED;
A database is created with the following characteristics:
Three control files are created as specified by the
CONTROL_FILES initialization parameter, which was set before database creation in the initialization parameter file. See "Sample Initialization Parameter File " and "Specifying Control Files ".
The password for user
pz6r58 and the password for
y1tz5p. The two clauses that specify the passwords for
SYSTEM are not mandatory in this release of Oracle Database. However, if you specify either clause, you must specify both clauses. For further information about the use of these clauses, see "Protecting Your Database: Specifying Passwords for Users SYS and SYSTEM".
The new database has three redo log files as specified in the
MAXLOGHISTORY define limits for the redo log. See Chapter 6, " Managing the Redo Log".
MAXDATAFILES specifies the maximum number of datafiles that can be open in the database. This number affects the initial sizing of the control file.
Note:You can set several limits during database creation. Some of these limits are limited by and affected by operating system limits. For example, if you set
For more information about setting limits during database creation, see the Oracle Database SQL Reference and your operating system specific Oracle documentation.
MAXINSTANCES specifies that only one instance can have this database mounted and open.
US7ASCII character set is used to store data in this database.
AL16UTF16 character set is specified as the
NATIONAL CHARACTER SET, used to store data in columns specifically defined as
SYSTEM tablespace, consisting of the operating system file
/u01/oracle/oradata/mynewdb/system01.dbf is created as specified by the
DATAFILE clause. If a file with that name already exists, it is overwritten.
SYSTEM tablespace is a locally managed tablespace. See "Creating a Locally Managed SYSTEM Tablespace".
SYSAUX tablespace is created, consisting of the operating system file
/u01/oracle/oradata/mynewdb/sysaux01.dbf as specified in the
SYSAUX DATAFILE clause. See "Creating the SYSAUX Tablespace".
TABLESPACE clause creates and names a default permanent tablespace for this database.
DEFAULT TEMPORARY TABLESPACE clause creates and names a default temporary tablespace for this database. See "Creating a Default Temporary Tablespace".
UNDO TABLESPACE clause creates and names an undo tablespace that is used to store undo data for this database if you have specified
UNDO_MANAGEMENT=AUTO in the initialization parameter file. See "Using Automatic Undo Management: Creating an Undo Tablespace".
Redo log files will not initially be archived, because the
ARCHIVELOG clause is not specified in this
DATABASE statement. This is customary during database creation. You can later use an
ALTER DATABASE statement to switch to
ARCHIVELOG mode. The initialization parameters in the initialization parameter file for
mynewdb relating to archiving are
LOG_ARCHIVE_FORMAT. See Chapter 7, " Managing Archived Redo Logs".
To make the database functional, you need to create additional files and tablespaces for users. The following sample script creates some additional tablespaces:
CONNECT SYS/password AS SYSDBA -- create a user tablespace to be assigned as the default tablespace for users CREATE TABLESPACE users LOGGING DATAFILE '/u01/oracle/oradata/mynewdb/users01.dbf' SIZE 25M REUSE AUTOEXTEND ON NEXT 1280K MAXSIZE UNLIMITED EXTENT MANAGEMENT LOCAL; -- create a tablespace for indexes, separate from user tablespace CREATE TABLESPACE indx LOGGING DATAFILE '/u01/oracle/oradata/mynewdb/indx01.dbf' SIZE 25M REUSE AUTOEXTEND ON NEXT 1280K MAXSIZE UNLIMITED EXTENT MANAGEMENT LOCAL;
For information about creating tablespaces, see Chapter 8, " Managing Tablespaces".
Run the scripts necessary to build views, synonyms, and PL/SQL packages:
CONNECT SYS/password AS SYSDBA @/u01/oracle/rdbms/admin/catalog.sql @/u01/oracle/rdbms/admin/catproc.sql EXIT
The following table contains descriptions of the scripts:
||Creates the views of the data dictionary tables, the dynamic performance views, and public synonyms for many of the views. Grants |
||Runs all scripts required for or used with PL/SQL.|
You may want to run other scripts. The scripts that you run are determined by the features and options you choose to use or install. Many of the scripts available to you are described in the Oracle Database Reference.
If you plan to install other Oracle products to work with this database, see the installation instructions for those products. Some products require you to create additional data dictionary tables. Usually, command files are provided to create and load these tables into the database data dictionary.
See your Oracle documentation for the specific products that you plan to install for installation and administration instructions.
Take a full backup of the database to ensure that you have a complete set of files from which to recover if a media failure occurs. For information on backing up a database, see Oracle Database Backup and Recovery Basics.
When you execute a
DATABASE statement, Oracle Database performs (at least) a number of operations. The actual operations performed depend on the clauses that you specify in the
DATABASE statement and the initialization parameters that you have set. Oracle Database performs at least these operations:
Creates the datafiles for the database
Creates the control files for the database
Creates the redo log files for the database and establishes the
SYSTEM tablespace and the
SYSTEM rollback segment
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
This section discusses several of the clauses of the
DATABASE statement. It expands upon some of the clauses discussed in "Step 7: Issue the CREATE DATABASE Statement" and introduces additional ones. Many of the
CREATE DATABASES clauses discussed here can be used to simplify the creation and management of your database.
The following topics are contained in this section:
The clauses of the
DATABASE statement used for specifying the passwords for users
If you omit these clauses, these users are assigned the default passwords
manager, respectively. A record is written to the alert file indicating that the default passwords were used. To protect your database, you should change these passwords using the
ALTER USER statement immediately after database creation.
Oracle strongly recommends that you specify these clauses, even though they are optional in this release of Oracle Database. The default passwords are commonly known, and if you neglect to change them later, you leave database vulnerable to attack by malicious users.
See Also:"Some Security Considerations"
When you specify the
EXTENT MANAGEMENT LOCAL clause in the
DATABASE statement, you cause Oracle Database to create a locally managed
SYSTEM tablespace, which is a tablespace for which the database determines and manages extent sizes. The
COMPATIBLE initialization parameter must be set to 9.2 or higher for this statement to be successful. If you do not specify the
EXTENT MANAGEMENT LOCAL clause, by default the database creates a dictionary-managed
Locally managed tablespaces provide better performance and greater ease of management than dictionary-managed tablespaces. A locally managed
SYSTEM tablespace is with
AUTOALLOCATE enabled by default, which means that the system determines and controls the number and size of extents. You may notice an increase in the initial size of objects created in a locally managed
SYSTEM tablespace because of the autoallocate policy. It is not possible to create a locally managed
SYSTEM tablespace and specify
UNIFORM extent size.
When you create your database with a locally managed
SYSTEM tablespace, ensure the following conditions are met:
A default temporary tablespace must exist, and that tablespace cannot be the
To meet this condition, you can specify the
TABLESPACE clause in the
DATABASE statement, or you can omit the clause and let Oracle Database create the tablespace for you using a default name and in a default location.
You must not create rollback segments in dictionary-managed tablespaces. Attempts to create rollback segments in a dictionary-managed tablespace will fail if the
SYSTEM tablespace is locally managed.
You can meet this condition by using automatic undo management. Oracle has deprecated the use of rollback segments. You can include the
UNDO TABLESPACE clause in the
DATABASE statement to create a specific undo tablespace. If you omit that clause, Oracle Database creates a locally managed undo tablespace for you using the default name and in a default location.
SYSTEM tablespace is locally managed, the following additional restrictions apply to other tablespaces in the database:
You cannot create any dictionary-managed tablespaces in the database.
You cannot migrate a locally managed tablespace to a dictionary-managed tablespace.
Preexisting dictionary-managed tablespaces can remain in the database, but only in read-only mode. They cannot be altered to read/write.
You can transport dictionary-managed tablespaces into the database, but you cannot set them to read/write.
Oracle Database lets you migrate an existing dictionary-managed
SYSTEM tablespace to a locally managed tablespace using the
DBMS_SPACE_ADMIN package. However, there is no procedure for backward migration.
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 and that you, as a DBA, must maintain. Other functionality or features that previously used the
SYSTEM tablespace can now use the
SYSAUX tablespace, thus reducing the load on the
You can specify only datafile attributes for the
SYSAUX tablespace, using the
SYSAUX DATAFILE clause in the
DATABASE statement. Mandatory attributes of the
SYSAUX tablespace are set by Oracle Database and include:
You cannot alter these attributes with an
TABLESPACE statement, and any attempt to do so will result in an error. You cannot drop or rename the
The size of the
SYSAUX tablespace is determined by the size of the database components that occupy
SYSAUX. See Table 2-2 for a list of all
SYSAUX occupants. Based on the initial sizes of these components, the
SYSAUX tablespace needs to be at least 240 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. For more information on how to manage the space consumption of the
SYSAUX tablespace on an ongoing basis, please refer to the "Managing the SYSAUX Tablespace".
If you include a
DATAFILE clause for the
SYSTEM tablespace, then you must specify the
SYSAUX DATAFILE clause as well, or the
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").
If you issue the
DATABASE statement with no other clauses, then the software creates a default database with datafiles for the
SYSAUX tablespaces stored in system-determined default locations, or where specified by an Oracle-managed files initialization parameter.
SYSAUX tablespace has the same security attributes as the
Note:This book discusses the creation of the
Table 2-2 lists the components that use the
SYSAUX tablespace as their default tablespace during installation, and the tablespace in which they were stored in earlier releases:
Table 2-2 Database Components and the SYSAUX Tablespace
|Component Using SYSAUX||Tablespace in Earlier Releases|
|Analytical Workspace Object Table|
|Enterprise Manager Repository|
|OLAP API History Tables|
|Oracle Data Mining|
|Oracle Ultra Search|
|Server Manageability Components||New in Oracle Database 10g|
|Unified Job Scheduler||New in Oracle Database 10g|
The installation procedures for these components provide the means of establishing their occupancy of the
See Also:"Managing the SYSAUX Tablespace" for information about managing the
The use of rollback segments for storing rollback information has been deprecated. Instead, you should use automatic undo management, which in turn uses an undo tablespace. Doing so requires the use of a different set of initialization parameters, and optionally, the inclusion of the
UNDO TABLESPACE clause in your
To enable automatic undo management mode, set the
UNDO_MANAGEMENT initialization parameter to
AUTO in your initialization parameter file. In this mode, rollback information, referred to as undo data, is stored in an undo tablespace rather than rollback segments and is managed by Oracle Database. If you want to define and name the undo tablespace yourself, you must also include the
UNDO TABLESPACE clause at database creation time. If you omit this clause, and automatic undo management is enabled, then the database creates a default undo tablespace named
TABLESPACE clause of the
DATABASE statement specifies a default permanent tablespace for the database. Oracle Database assign to this tablespace any non-
SYSTEM users for whom you do not explicitly specify a different permanent tablespace. If you do not specify this clause, then the
SYSTEM tablespace is the default permanent tablespace for non-
SYSTEM users. Oracle strongly recommends that you create a default permanent tablespace.
See Also:Oracle Database SQL Reference for the syntax of the
DEFAULT TEMPORARY TABLESPACE clause of the
DATABASE statement creates a default temporary tablespace for the database. Oracle Database this tablespace as the temporary tablespace for users who are not explicitly assigned a temporary tablespace.
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
Note:When you specify a locally managed
You can add or the default temporary tablespace after database creation. You do this by creating a new temporary tablespace or tablespace group with a
CREATE TEMPORARY TABLESPACE statement, and then assign it as the temporary tablespace using the
ALTER DATABASE DEFAULT TEMPORARY TABLESPACE statement. Users will automatically be switched (or assigned) to the new default temporary tablespace.
The following statement assigns a new default temporary tablespace:
ALTER DATABASE DEFAULT TEMPORARY TABLESPACE tempts2;
The new default temporary tablespace must already exist. When using a locally managed
SYSTEM tablespace, the new default temporary tablespace must also be locally managed.
You cannot drop or take offline a default temporary tablespace, but you can assign a new default temporary tablespace and then drop or take offline the former one. You cannot change a default temporary tablespace to a permanent tablespace.
Users can obtain the name of the current default temporary tablespace by querying the
PROPERTY_VALUE columns of the
DATABASE_PROPERTIES view. These columns contain the values "
DEFAULT_TEMP_TABLESPACE" and the default temporary tablespace name, respectively.
You can minimize the number of clauses and parameters that you specify in your
DATABASE statement by using the Oracle-managed files feature. You do this either by specifying a directory in which your files are created and managed by Oracle Database, or by using Automatic Storage Management. When you use Automatic Storage Management, you specify a disk group in which the database creates and manages your files, including file redundancy and striping.
By including any of the initialization parameters
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
Redo log files
Archive log files
Block change tracking files
See Also:"Specifying a Flash Recovery Area" for information about setting initialization parameters that create a flash recovery area
DATABASE statement shows briefly how the Oracle-managed files feature works, assuming you have specified required initialization parameters:
CREATE DATABASE rbdb1 USER SYS IDENTIFIED BY pz6r58 USER SYSTEM IDENTIFIED BY y1tz5p UNDO TABLESPACE undotbs DEFAULT TEMPORARY TABLESPACE tempts1;
DATAFILE clause is specified, so the database creates an Oracle-managed datafile for the
LOGFILE clauses are included, so the database creates two Oracle-managed redo log file groups.
SYSAUX DATAFILE is included, so the database creates an Oracle-managed datafile for the
DATAFILE subclause is specified for the
UNDO TABLESPACE clause, so the database creates an Oracle-managed datafile for the undo tablespace.
TEMPFILE subclause is specified for the
DEFAULT TEMPORARY TABLESPACE clause, so the database creates an Oracle-managed tempfile.
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 (see "Managing Initialization Parameters Using a Server Parameter File"), the database automatically sets the appropriate initialization parameters.
Oracle Database simplifies management of tablespaces and enables support for ultra-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 datafiles 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
DATABASE statement that let you include support for bigfile tablespaces.
See Also:"Bigfile Tablespaces" for more information about bigfile tablespaces
SET DEFAULT ... TABLESPACE clause of the
DATABASE statement to determines the default type of tablespace for this database in subsequent
TABLESPACE statements. Specify either
SET DEFAULT BIGFILE TABLESPACE or
SET DEFAULT SMALLFILE TABLESPACE. If you omit this clause, 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 datafiles completely transparent for users. SQL syntax for the
TABLESPACE statement has been extended to allow you to perform operations on tablespaces, rather than the underlying datafiles.
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 rbdb1 USER SYS IDENTIFIED BY pz6r58 USER SYSTEM IDENTIFIED BY y1tz5p SET DEFAULT BIGFILE TABLESPACE UNDO TABLESPACE undotbs DEFAULT TEMPORARY TABLESPACE tempts1;
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';
SYSAUX tablespaces are always created with the default tablespace type. However, you can explicitly override the default tablespace type for the
TEMPORARY tablespace during the
CREATE DATABASE rbdb1 ... BIGFILE UNDO TABLESPACE undotbs DATAFILE '/u01/oracle/oradata/mynewdb/undotbs01.dbf' SIZE 200M REUSE AUTOEXTEND ON MAXSIZE UNLIMITED;
CREATE DATABASE rbdb1 SET DEFAULT BIGFILE TABLSPACE ... SMALLFILE DEFAULT TEMPORARY TABLESPACE tempts1 TEMPFILE '/u01/oracle/oradata/mynewdb/temp01.dbf' SIZE 20M REUSE ...
Oracle Database lets you specify the database default time zone and lets you choose the supporting time zone file.
You set the database default time zone by specifying the
SET TIME_ZONE clause of the
CREATE DATABASE statement. If omitted, the default database time zone is the operating system time zone. The database time zone can be changed for a session with an
ALTER SESSION statement.
See Also:Oracle Database Globalization Support Guide for more information about setting the database time zone
This section provides information on the time zone files used to support the database time zone, specifically on Solaris platforms. Names of directories, filenames, and environment variables may differ for on other platforms but will probably be the same for all UNIX platforms.
Two time zone files are provided in the Oracle Database installation directory:
This is the default file. It contains the most commonly used time zones and is smaller, thus enabling better database performance.
This file contains a larger set of defined time zones and should be used if you require zones that are not defined in the default
timezone.dat file. Use of this larger set of time zone information can affect performance.
To enable the use of the larger time zone datafile, do the following:
Shut down the database.
Restart the database.
Once the larger
timezlrg.dat is used, it must continue to be used unless you are sure that none of the nondefault zones are used for data that is stored in the database. Also, all databases that share information must use the same time zone datafile.
Offset from UTC (formerly GMT)
Transition times for daylight savings
Abbreviation for standard time
Abbreviation for daylight savings time
SELECT * FROM V$TIMEZONE_NAMES;
The time zone names contained in both the larger and smaller time zone files are listed in the Oracle Database Globalization Support Guide.
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.
See Also:Oracle Database SQL Reference for information about operations that can be done in
To put the database into
FORCE LOGGING mode, use the
FORCE LOGGING clause in the
CREATE DATABASE statement. If you do not specify this clause, the database is not placed into
FORCE LOGGING mode.
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.
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:"Controlling the Writing of Redo Records" for information about using the
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.
Oracle Database has provided generally appropriate values in the sample initialization parameter file provided with your database software or created for you by the Database Configuration Assistant. 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. For any relevant initialization parameters not specifically included in the initialization parameter file, the database supplies defaults.
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 traditional text initialization parameter file, 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, initialization parameter file changes made by the
ALTER SYSTEM statement can persist across shutdown and startup. This is discussed in "Managing Initialization Parameters Using a Server Parameter File".
The following topics are contained in this section:
See Also:Oracle Database Reference for descriptions of all initialization parameters including their default settings
The global database name consists of the user-specified local database name and the location of the database within a network structure. The
DB_NAME initialization parameter determines the local name component of the database name, and the
DB_DOMAIN parameter 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.acme.com, edit the parameters of the new parameter file as follows:
DB_NAME = test DB_DOMAIN = us.acme.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_DOMAIN initialization parameters and re-creating the control file.
See Also:Oracle Database Utilities for information about using the
DB_NAME must be set to a text string of no more than eight characters. During database creation, the name provided for
DB_NAME is recorded in the datafiles, 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 not the same, the database does not start.
DB_DOMAIN is a text string that specifies the network domain where the database is created. This is typically the name of the organization that owns the database. If the database you are about to create will ever be part of a distributed database system, give special attention to this initialization parameter before database creation.
See Also:Part VII, " Distributed Database Management " for more information about distributed databases
A flash 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 Oracle-managed current database files (datafiles, control files, and online redo logs).
You specify a flash recovery area with the following initialization parameters:
DB_RECOVERY_FILE_DEST: Location of the flash recovery area. This can be a directory, file system, or Automatic Storage Management (ASM) disk group. It cannot be a raw file system.
In a RAC environment, this location must be on a cluster file system, 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 flash recovery area. This initialization parameter must be specified before
DB_RECOVERY_FILE_DEST is enabled.
In a 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_DUPLEX_DEST parameters. You must disable those parameters before setting up the flash recovery area. You can instead set values for the
n parameters. If you do not set values for local
n, then setting up the flash recovery area will implicitly set
LOG_ARCHIVE_DEST_10 to the flash recovery area.
Oracle recommends using a flash recovery area, because it can simplify backup and recovery operations for your database.
See Also:Oracle Database Backup and Recovery Basics to learn how to create and use a flash recovery area
CONTROL_FILES initialization parameter specifies one or more control filenames for the database. When you execute the
CREATE DATABASE statement, the control files listed in the
CONTROL_FILES parameter are created.
If do not include
CONTROL_FILES in the initialization parameter file, then Oracle Database creates a control file using a default operating system dependent filename or, if you have enabled Oracle-managed files, creates Oracle-managed control files .
If you want the database to create new operating system files when creating database control files, the filenames listed in the
CONTROL_FILES parameter must not match any filenames 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 filenames listed in the
CONTROL_FILES parameter match the filenames that are to be reused.
DB_BLOCK_SIZE initialization parameter specifies the standard block size for the database. 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.
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 need to specify. Typically,
DB_BLOCK_SIZE is set to either 4K or 8K. If you do not set a value for this parameter, 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, 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:
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.
Tablespaces of nonstandard block sizes can be created using the
CREATE TABLESPACE statement and specifying the
BLOCKSIZE clause. 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 the next section, "Managing the System Global Area (SGA) ".
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.
This section discusses the initialization parameters that affect the amount of memory allocated to the System Global Area (SGA). Except for the
SGA_MAX_SIZE initialization parameter, they are dynamic parameters whose values can be changed by the
ALTER SYSTEM statement. The size of the SGA is dynamic, and can grow or shrink by dynamically altering these parameters.
This section contains the following topics:
The SGA comprises a number of memory components, which are pools of memory used to satisfy a particular class of memory allocation requests. Examples of memory components include the shared pool (used to allocate memory for SQL and PL/SQL execution), the java pool (used for java objects and other java execution memory), and the buffer cache (used for caching disk blocks). All SGA components allocate and deallocate space in units of granules. Oracle Database tracks SGA memory use in internal numbers of granules for each SGA component.
The memory for dynamic components in the SGA is allocated in the unit of granules. Granule size is determined by total SGA size. Generally speaking, on most platforms, if the total SGA size is equal to or less than 1 GB, then granule size is 4 MB. For SGAs larger than 1 GB, granule size is 16 MB. Some platform dependencies may arise. For example, on 32-bit Windows NT, the granule size is 8 MB for SGAs larger than 1 GB. Consult your operating system specific documentation for more details.
You can query the
V$SGAINFO view to see the granule size that is being used by an instance. The same granule size is used for all dynamic components in the SGA.
If you specify a size for a component that is not a multiple of granule size, Oracle Database rounds the specified size up to the nearest multiple. For example, if the granule size is 4 MB and you specify
DB_CACHE_SIZE as 10 MB, the database actually allocates 12 MB.
SGA_MAX_SIZE initialization parameter specifies the maximum size of the System Global Area for the lifetime of the instance. You can dynamically alter the initialization parameters affecting the size of the buffer caches, shared pool, large pool, Java pool, and streams pool but only to the extent that the sum of these sizes and the sizes of the other components of the SGA (fixed SGA, variable SGA, and redo log buffers) does not exceed the value specified by
If you do not specify
SGA_MAX_SIZE, then Oracle Database selects a default value that is the sum of all components specified or defaulted at initialization time. If you do specify
SGA_MAX_SIZE, and at the time the database is initialized the value is less than the sum of the memory allocated for all components, either explicitly in the parameter file or by default, then the database ignores the setting for
You enable the automatic shared memory management feature by setting the
SGA_TARGET parameter. This parameter in effect replaces the parameters that control the memory allocated for a specific set of individual components, which are now automatically managed. In addition, you must ensure that the
STATISTICS_LEVEL initialization parameter is set to
TYPICAL (the default) or
SGA_TARGET initialization parameter reflects the total size of the SGA. Table 2-3 lists the SGA components for which
SGA_TARGET includes memory and the initialization parameters corresponding to those components.
Table 2-3 Automatically Sized SGA Components and Corresponding Parameters
|SGA Component||Initialization Parameter|
|Fixed SGA and other internal allocations needed by the Oracle Database instance||NA|
|The shared pool|
|The large pool|
|The Java pool|
|The buffer cache|
Table 2-4 Manually Sized SGA Components that Use SGA_TARGET Space
|SGA Component||Initialization Parameter|
|The log buffer|
|The keep and recycle buffer caches|
|Nonstandard block size buffer caches|
|The Streams pool|
When you are migrating from a manual management scheme, execute the following query on the instance running in manual mode to get a value for
SELECT ( (SELECT SUM(value) FROM V$SGA) - (SELECT CURRENT_SIZE FROM V$SGA_DYNAMIC_FREE_MEMORY) ) "SGA_TARGET" FROM DUAL;
You can then remove the parameters that formerly controlled memory for the now automatically sized components.
For example, suppose you currently have the following configuration of parameters on a manual mode instance with
SGA_MAX_SIZE set to 1200M:
SHARED_POOL_SIZE = 200M
DB_CACHE_SIZE = 500M
Also assume that the result of the queries is as follows:
SELECT SUM(value) FROM V$SGA = 1200M SELECT CURRENT_VALUE FROM V$SGA_DYNAMIC_FREE_MEMORY = 208M
You can take advantage of automatic shared memory management by replacing the manually sized parameters (
LARGE_POOL_SIZE) with the following setting:
SGA_TARGET = 992M
where 992M = 1200M minus 208M.
By default, when you set a value for
SGA_TARGET, the value of the parameters corresponding to all the automatically sized SGA components is set to zero. However, you can still exercise some control over the size of the automatically sized components by specifying minimum values for the parameters corresponding to these components. Doing so can be useful if you know that an application cannot function properly without a minimum amount of memory in specific components. You specify the minimum amount of SGA space for a component by setting a value for its corresponding initialization parameter. Here is an example configuration:
SGA_TARGET = 256M
SHARED_POOL_SIZE = 32M
DB_CACHE_SIZE = 100M
In this example, the shared pool and the default buffer pool will not be sized smaller than the specified values (32 M and 100M, respectively). The remaining 124M (256 minus 132) is available for use by all the manually and automatically sized components.
The actual distribution of values among the SGA components might look like this:
Actual shared pool size = 64M
Actual buffer cache size = 128M
Actual Java pool size = 60M
Actual large pool size = 4M
The parameter values determine the minimum amount of SGA space allocated. The fixed view
V$SGA_DYNAMIC_COMPONENTS displays the current actual size of each SGA component. You can also see the current actual values of the SGA components in the Enterprise Manager memory configuration page.
Manually limiting the minimum size of one or more automatically sized components reduces the total amount of memory available for dynamic adjustment. This reduction in turn limits the ability of the system to adapt to workload changes. Therefore, this practice is not recommended except in exceptional cases. The default automatic management behavior maximizes both system performance and the use of available resources.
When the automatic shared memory management feature is enabled, the internal tuning algorithm tries to determine an optimal size for the shared pool based on the workload. It usually converges on this value by increasing in small increments over time. However, the internal tuning algorithm typically does not attempt to shrink the shared pool, because the presence of open cursors, pinned PL/SQL packages, and other SQL execution state in the shared pool make it impossible to find granules that can be freed. Therefore, the tuning algorithmn only tries to increase the shared pool in conservative increments, starting from a conservative size and stabilizing the shared pool at a size that produces the optimal performance benefit.
You can modify the value of
SGA_TARGET and the parameters controlling individual components dynamically using the
ALTER SYSTEM statement, as described in the sections that follow.
SGA_TARGET parameter can be increased up to the value specified for the
SGA_MAX_SIZE parameter, and it can also be reduced. If you reduce the value of
SGA_TARGET, the system identifies one or more automatically tuned components to release memory. You can reduce
SGA_TARGET until one or more automatically tuned components reach their minimum size. Oracle Database determines the minimum allowable value for
SGA_TARGET taking into account several factors, including values set for the automatically sized components, manually sized components that use
SGA_TARGET space, and number of CPUs.
The change in the amount of physical memory consumed when
SGA_TARGET is modified depends on the operating system. On some UNIX platforms that do not support dynamic shared memory, the physical memory in use by the SGA is equal to the value of the
SGA_MAX_SIZE parameter. On such platforms, there is no real benefit in setting
SGA_TARGET to a value smaller than
SGA_MAX_SIZE. Therefore, setting
SGA_MAX_SIZE on those platforms is not recommended.
On other platforms, such as Solaris and Windows, the physical memory consumed by the SGA is equal to the value of
SGA_TARGET is resized, the only components affected are the automatically tuned components for which you have not set a minimum value in their corresponding initialization parameter. Any manually configured components remain unaffected.
For example, suppose you have an environment with the following configuration:
SGA_MAX_SIZE = 1024M
SGA_TARGET = 512M
DB_8K_CACHE_SIZE = 128M
In this example, the value of
SGA_TARGET can be resized up to 1024M and can also be reduced until one or more of the buffer cache, shared pool, large pool, or java pool reaches its minimum size. The exact value depends on environmental factors such as the number of CPUs on the system. However, the value of
DB_8K_CACHE_SIZE remains fixed at all times at 128M
SGA_TARGET is reduced, if the values for any automatically tuned component sizes has been specified to limit their minimum sizes, then those components will not be reduced smaller than that minimum. Consider the following combination of parameters:
SGA_MAX_SIZE = 1024M
SGA_TARGET = 512M
DB_CACHE_SIZE = 96M
DB_8K_CACHE_SIZE = 128M
As in the last example, if
SGA_TARGET is reduced, the
DB_8K_CACHE_SIZE parameter is permanently fixed at 128M. In addition, the primary buffer cache (determined by the
DB_CACHE_SIZE parameter) will not be reduced smaller than 96M. Thus the amount that
SGA_TARGET can be reduced is restricted.
SGA_TARGET is not set, the automatic shared memory management feature is not enabled. Therefore the rules governing resize for all component parameters are the same as in earlier releases. However, when automatic shared memory management is enabled, the manually specified sizes of automatically sized components serve as a lower bound for the size of the components. You can modify this limit dynamically by changing the values of the corresponding parameters.
If the specified lower limit for the size of a given SGA component is less than its current size, there is no immediate change in the size of that component. The new setting only limits the automatic tuning algorithm to that reduced minimum size in the future. For example, consider the following configuration:
SGA_TARGET = 512M
LARGE_POOL_SIZE = 256M
Current actual shared pool size = 284M
In this example, if you increase the value of
LARGE_POOL_SIZE to a value greater than the actual current size of the component, the system expands the component to accommodate the increased minimum size. For example, if you increase the value of
LARGE_POOL_SIZE to 300M, then the system increases the large pool until it reaches 300M. This resizing occurs at the expense of one or more automatically tuned components.
If you decrease the value of
LARGE_POOL_SIZE to 200, there is no immediate change in the size of that component. The new setting only limits the reduction of the large pool size to 200 M in the future.
Parameters for manually sized components can be dynamically altered as well. However, rather than setting a minimum size, the value of the parameter specifies the precise size of the corresponding component. When you increase the size of a manually sized component, extra memory is taken away from one or more automatically sized components. When you decrease the size of a manually sized component, the memory that is released is given to the automatically sized components.
For example, consider this configuration:
SGA_TARGET = 512M
DB_8K_CACHE_SIZE = 128M
In this example, increasing
DB_8K_CACHE_SIZE by 16 M to 144M means that the 16M will be taken away from the automatically sized components. Likewise, reducing
DB_8K_CACHE_SIZE by 16M to 112M means that the 16M will be given to the automatically sized components.
If you decide not to use automatic shared memory management by not setting the
SGA_TARGET parameter, you must manually configure each component of the SGA. This section provides guidelines on setting the parameters that control the size of each SGA components.
The buffer cache initialization parameters determine the size of the buffer cache component of the SGA. You use them to specify the sizes of caches for the various block sizes used by the database. These initialization parameters are all dynamic.
If you intend to use multiple block sizes in your database, you must have the
DB_CACHE_SIZE and at least one
K_CACHE_SIZE parameter set. Oracle Database assigns an appropriate default value to the
DB_CACHE_SIZE parameter, but the
K_CACHE_SIZE parameters default to 0, and no additional block size caches are configured.
The size of a buffer cache affects performance. Larger cache sizes generally reduce the number of disk reads and writes. However, a large cache may take up too much memory and induce memory paging or swapping.
DB_CACHE_SIZE initialization parameter has replaced the
DB_BLOCK_BUFFERS initialization parameter, which was used in earlier releases. The
DB_CACHE_SIZE parameter specifies the size in bytes of the cache of standard block size buffers. Thus, to specify a value for
DB_CACHE_SIZE, you would determine the number of buffers that you need and multiple that value times the block size specified in
For backward compatibility, the
DB_BLOCK_BUFFERS parameter still functions, but it remains a static parameter and cannot be combined with any of the dynamic sizing parameters.
The sizes and numbers of nonstandard block size buffers are specified by the following initialization parameters:
Each parameter specifies the size of the buffer cache for the corresponding block size. For example:
DB_BLOCK_SIZE=4096 DB_CACHE_SIZE=12M DB_2K_CACHE_SIZE=8M DB_8K_CACHE_SIZE=4M
In this example, the parameters specify that the standard block size of the database is 4K. The size of the cache of standard block size buffers is 12M. Additionally, 2K and 8K caches will be configured with sizes of 8M and 4M respectively.
Note:You cannot use a
SHARED_POOL_SIZE initialization parameter is a dynamic parameter that lets you specify or adjust the size of the shared pool component of the SGA. Oracle Database selects an appropriate default value. Configuring the shared pool is discussed in Oracle Database Performance Tuning Guide.
LARGE_POOL_SIZE initialization parameter is a dynamic parameter that lets you specify or adjust the size of the large pool component of the SGA. The large pool is an optional component of the SGA. You must specifically set the
LARGE_POOL_SIZE parameter if you want to create a large pool. Configuring the large pool is discussed in Oracle Database Performance Tuning Guide.
JAVA_POOL_SIZE initialization parameter is a dynamic parameter that lets you specify or adjust the size of the java pool component of the SGA. Oracle Database selects an appropriate default value. Configuration of the java pool is discussed in Oracle Database Java Developer's Guide.
STREAMS_POOL_SIZE initialization parameter is a dynamic parameter that lets you specify or adjust the size of the Streams pool component of the SGA. If
STREAMS_POOL_SIZE is set to 0, then the Oracle Streams product will use the shared pool to satisfy its SGA memory requirements. Configuration of the Streams pool is discussed in Oracle Streams Concepts and Administration.
The following views provide information about the SGA components and their dynamic resizing:
||Displays summary information about the system global area (SGA).|
||Displays size information about the SGA, including the sizes of different SGA components, the granule size, and free memory.|
||Displays detailed information about the SGA.|
||Displays information about the dynamic SGA components. This view summarizes information based on all completed SGA resize operations since instance startup.|
||Displays information about the amount of SGA memory available for future dynamic SGA resize operations.|
||Displays information about the last 400 completed SGA resize operations.|
||Displays information about SGA resize operations that are currently in progress. A resize operation is an enlargement or reduction of a dynamic SGA component.|
PROCESSES initialization parameter determines the maximum number of operating system processes that can be connected to Oracle Database concurrently. 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, you will have additional background processes. If you are using Automatic Storage Management, then add three additional processes.
If you plan on running 50 user processes, a good estimate would be to set the
PROCESSES initialization parameter to 60.
Every Oracle Database must have a method of maintaining information that is used to roll back, or 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.
The use of manual undo management mode, which stores undo data in rollback segments, has been deprecated. This section provides instructions for setting up an environment for automatic undo management using an undo tablespace. An undo tablespace is easier to administer than rollback segments, and automatic undo management lets you explicitly set a retention guarantee time.
UNDO_MANAGEMENT initialization parameter determines whether an instance will start up in automatic undo management mode, which stores undo in an undo tablespace, or manual undo management mode, which stores undo in rollback segments. By default, this parameter is set to
MANUAL. Set this parameter to
AUTO to enable automatic undo management mode.
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 undo management mode, then the default undo tablespace--either the system-created
SYS_UNDOTS 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 has been specified during database creation or by the
UNDO_TABLESPACE initialization parameter, then the instance will start. However, it uses the
SYSTEM rollback segment for storage of undo data. This use of the
SYSTEM rollback segment is not recommended in normal circumstances, and an alert message is written to the alert file to warn that the system is running without an undo tablespace. ORA-01552 errors are issued for any attempts to write non-
SYSTEM related undo data to the
SYSTEM rollback segment.
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 10g database, but specify
COMPATIBLE = 18.104.22.168 in the initialization parameter file, then features that requires 10.0 compatibility will generate an error if you try to use them. Such a database is said to be at the 22.214.171.124 compatibility level.
You can advance the compatibility level of your database. If you do advance the compatibility of your database with the
COMPATIBLE initialization parameter, 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.
Caution:For Oracle Database 10g Release 1 (10.1), the default value of the
Note:Oracle no longer offers licensing by the number of concurrent sessions. Therefore the
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, as shown in the following example:
LICENSE_MAX_USERS = 200
If database creation fails, you can look at the alert log to determine the reason for the failure and to determine corrective action. The alert log is discussed in "Monitoring the Operation of Your Database".
You should shut down the instance and delete any files created by the
CREATE DATABASE statement before you attempt to create it again. After correcting the error that caused the failure of the database creation, try re-creating the database.
Dropping a database involves removing its datafiles, redo log files, control files, and initialization parameter files. The
DROP DATABASE statement deletes all control files and all other database files listed in the control file. To use the
DROP DATABASE statement successfully, all of the following conditions must apply:
The database must be mounted and closed.
The database must be mounted exclusively--not in shared mode.
The database must be mounted as
An example of this statement is:
DROP DATABASE statement has no effect on archived 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 the database is on raw disks, the actual raw disk special files are not deleted.
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.
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. This section introduces the server parameter file, and explains how to manage initialization parameters using either method of storing the parameters. The following topics are contained in this section.
A server parameter file (
SPFILE) can be thought of as a repository for initialization parameters that is maintained on the machine 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 changes effected by
ALTER SYSTEM statements persistent. It also provides a basis for self-tuning by the Oracle Database server.
A server parameter file is initially built from a traditional text initialization parameter file using the
CREATE SPFILE statement. It is a binary file that cannot be edited using a text editor. Oracle Database provides other interfaces for viewing and modifying parameter settings.
Caution: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.
At system startup, the default behavior of the
STARTUP command is to read a server parameter file to obtain initialization parameter settings. The
STARTUP command with no
PFILE clause reads the server parameter file from an operating system specific location. If you use a traditional text initialization parameter file, you must specify the
PFILE clause when issuing the
STARTUP command. Instructions for starting an instance using a server parameter file are contained in "Starting Up a Database".
If you are currently using a traditional initialization parameter file, use the following steps to migrate to a server parameter file.
If the initialization parameter file is located on a client machine, transfer the file (for example, FTP) from the client machine to the server machine.
Note:If you are migrating to a server parameter file in an Oracle Real Application Clusters environment, you must combine all of your instance-specific initialization parameter files into a single initialization parameter file. Instructions for doing this, and other actions unique to using a server parameter file for instances that are part of an Oracle Real Application Clusters installation, are discussed in:
Create a server parameter file using the
CREATE SPFILE statement. This statement reads the initialization parameter file to create a server parameter file. The database does not have to be started to issue a
CREATE SPFILE statement.
Start up the instance using the newly created server parameter file.
The server parameter file is initially created from a traditional text initialization parameter file. It must be created prior to its use in the
STARTUP command. The
CREATE SPFILE statement is used to create a server parameter file. You must have the
SYSDBA or the
SYSOPER system privilege to execute this statement.
The following example creates a server parameter file from initialization parameter file
/u01/oracle/dbs/init.ora. In this example no
SPFILE name is specified, so the file is created in a platform-specific default location and is named
CREATE SPFILE FROM PFILE='/u01/oracle/dbs/init.ora';
Another example, which follows, illustrates creating a server parameter file and supplying a name.
CREATE SPFILE='/u01/oracle/dbs/test_spfile.ora' FROM PFILE='/u01/oracle/dbs/test_init.ora';
When you create a server parameter file from an initialization parameter file, comments specified on the same lines as a parameter setting in the initialization parameter file are maintained in the server parameter file. All other comments are ignored.
The server parameter file is always created on the machine running the database server. If a server parameter file of the same name already exists on the server, it is overwritten with the new information.
Oracle recommends that you allow the database server to default the name and location of the server parameter file. This will ease administration of your database. For example, the
STARTUP command assumes this default location to read the parameter file. The table that follows shows the default name and location of the server parameter file. The table assumes that the
SPFILE is a file. If it is a raw device, the default name could be a logical volume name or partition device name, and the default location could differ.
|Platform||Default Name||Default Location|
If you create a server parameter file in a location other than the default location, then you must create a parameter file with the default parameter file name in the default location that points to the user-generated
SPFILE. The parameter file would contain one line:
SPFILE = 'location'
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.
Note:When you use the Database Configuration Assistant to create a database, it can automatically create a server parameter file for you.
SPFILE initialization parameter contains the name of the current server parameter file. When the default server parameter file is used by the server (that is, you issue a
STARTUP command and do not specify a
PFILE), 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.
SPFILE parameter can also be set in a traditional parameter file to indicate the server parameter file to use. You use the
SPFILE parameter to specify a server parameter file located in a nondefault location. Do not use an
IFILE initialization parameter within a traditional initialization parameter file to point to a server parameter file; instead, use the
SPFILE parameter. See "Starting Up a Database" for details about:
Starting up a database that uses a server parameter file
SPFILE parameter to specify the name of a server parameter file to use at instance startup
ALTER SYSTEM statement lets you set, change, or restore to default the values of initialization parameter. If you are using a traditional 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 initialization parameters on disk. You must update them manually to be passed to a future instance. Using a server parameter file overcomes this limitation.
||The change is applied in the server parameter file only. The effect is as follows:
||The change is applied in memory only. The effect is as follows:
||The change is applied in both the server parameter file and memory. The effect is as follows:
It is an error to specify
SCOPE=BOTH if the server is not using 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 traditional 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.
COMMENT clause lets you associate a text string with the parameter update. When you specify
BOTH, the comment is written to the server parameter file.
The following statement changes the maximum number of job queue processes allowed for the instance. It includes a comment, and explicitly states that the change is to be made only in memory (that is, it is not persistent across instance shutdown and startup).
ALTER SYSTEM SET JOB_QUEUE_PROCESSES=50 COMMENT='temporary change on Nov 29' SCOPE=MEMORY;
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 of create a new archive destination.
ALTER SYSTEM SET LOG_ARCHIVE_DEST_4='LOCATION=/u02/oracle/rbdb1/',MANDATORY,'REOPEN=2' COMMENT='Add new destimation 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.
If an initialization parameter takes a value that is a string, you can restore the value to its default value by using empty single quote marks, as follows:
ALTER SYSTEM SET parameter = '';
For numeric and boolean value parameters, you must explicitly set the parameter back to its original default value.
You can use the
CREATE PFILE statement to export a server parameter file to a traditional text initialization parameter file. Doing so might be necessary for several reasons:
To create backups of the server parameter file
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 the
To modify the &spfile;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
You must have the
SYSDBA or the
SYSOPER system privilege to execute the
CREATE PFILE statement. The exported file is created on the database server machine. 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 server parameter file:
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';
You can create a backup of your server parameter file by exporting it, as described in "Exporting the Server Parameter File". If the backup and recovery strategy for your database is implemented using Recovery Manager (RMAN), then you can use RMAN to create a backup. The server parameter file is backed up automatically by RMAN when you back up your database, but RMAN also lets you specifically create a backup of the currently active server parameter file.
If an error occurs while reading the server parameter file (during startup or an export operation), or while writing the server parameter file during its creation, the operation terminates with an error reported to the user.
If an error occurs while reading or writing the server parameter file during a parameter update, the error is reported in the alert file 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 then restart the instance.
Continue to run the database if you do not care that subsequent parameter updates will not be persistent.
||This SQL*Plus command displays the values of parameters currently in use.|
||This SQL statement creates a text initialization parameter file from the binary server parameter file.|
||This view displays the values of parameters currently in effect.|
||This view displays the values of parameters currently in effect. It is easier to distinguish list parameter values in this view because each list parameter value appears as a row.
I think this means "For parameters with multiple attributes, this view displays each attribute on a separate row." DL
||This view displays the current contents of the server parameter file. The view returns |
See Also:Oracle Database Reference for a complete description of views
This section describes Oracle Database 10g services and includes the following topics:
Services are logical abstractions for managing workloads in Oracle Database 10g. Services divide workloads into mutually disjoint groupings. Each 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 service for each responsibility, such as general ledger, accounts receivable, order entry, and so on.
In Oracle Database 10g, services are built into the Oracle Database providing single system image for workloads, prioritization for workloads, performance measures for real transactions, and alerts and actions when performance goals are violated. Services enable you to configure a workload, 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), Net Configuration Assistant (NetCA), and Enterprise Manager (EM). Enterprise Manager supports viewing and operating services as a whole, with drill down to the instance-level when needed.
In Real Application Clusters (RAC), a service can span one or more instances and facilitate real workload balancing based on real transaction performance. This provides end-to-end unattended recovery, rolling changes by workload, and full location transparency. RAC also enables you to manage a number of service features with Enterprise Manager, the DBCA, and the Server Control utility (SRVCTL).
Services also 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 services, workloads are visible and measurable. Resource consumption and waits are attributable by application. Additionally, resources assigned to 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, services are measured automatically and the performance is compared to service-level thresholds. Performance violations are reported to Enterprise Manager, enabling the execution of automatic or scheduled solutions.
See Also:Oracle Real Application Clusters Deployment and Performance Guide for more information about services in RAC
Installations configure Oracle Database 10g services in the database giving each service a unique global name, associated performance goals, and associated importance. The services are tightly integrated with the Oracle Database and are maintained in the data dictionary. You can find service information in the following service-specific views:
The following additional views also contain some information about services:
See Also:Oracle Database Reference for detailed information about these views
Several Oracle Database features support services. The Automatic Workload Repository (AWR) manages the performance of services. AWR records service performance, including execution times, wait classes, and resources consumed by service. AWR alerts warn when service response time thresholds are exceeded. The dynamic views report current service performance metrics with one hour of history. Each service has quality-of-service thresholds for response time and CPU consumption.
In addition, the Database Resource Manager maps services to consumer groups. This enables you to automatically manage the priority of one service relative to others. You can use consumer groups to define relative priority in terms of either ratios or resource consumption. This is described in more detail, for example, in Oracle Real Application Clusters Deployment and Performance Guide.
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. For Oracle*Applications, ERP, CRM, and iSupport functions create a functional division of the work. For SAP, dialog and update functions create a functional division of the work.
In contrast, data-dependent routing routes sessions to services based on data keys. The mapping of work requests to services occurs in the object relational mapping layer for application servers and TP monitors. For example, in RAC, these ranges can be completely dynamic and based on demand because the database is shared.
You can also define preconnect application services in RAC databases. Preconnect services span instances to support a service in the event of a failure. The preconnect service supports TAF preconnect mode and is managed transparently when using RAC.
In addition to application services, Oracle Database also supports two internal services:
SYS$BACKGROUND is used by the background processes only and
SYS$USERS is the default service for user sessions that are not associated with services.
DBMS_SERVICE package or set the
SERVICE_NAMES parameter to create application services on a single-instance Oracle Database. You can later define the response time goal or importance of each service through EM, either individually or by using the Enterprise Manager feature "Copy Thresholds From a Baseline" on the Manage Metrics/Edit Threshold pages. You can also do this using PL/SQL.
Using services requires no changes to your application code. Client-side work connects to a service. Server-side work specifies the service when creating the job class for the Job Scheduler and the database links for distributed databases. Work requests executing under a service inherit the performance thresholds for the service and are measured as part of the service.
Middle-tier applications and client-server applications use a service by specifying the service as part of the connection in TNS connect data. This connect data may be in the TNSnames file for thick Net drivers, in the URL specification for thin drivers, or may be maintained in the Oracle Internet Directory. For example, data sources for the Oracle Application Server 10g are set to route to a service. Using Net Easy*Connection in Oracle Database 10g, this connection needs only the service and network address, for example,
hr/hr@//myVIP/myservice. For Oracle E-Business Suite, the service is also maintained in the application database identifier and in the cookie for the ICX parameters.
Server-side work, such as the Job Scheduler, parallel execution, and Oracle Streams Advanced Queuing, set the service name as part of the workload definition.
For the Job Scheduler, the service that the job class uses is defined when the job class is created. During execution, jobs are assigned to job classes, and job classes run within services. Using 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 service just like any other client. The parallel query processes inherit the service for the duration of the execution. At the end of query execution, the parallel execution processes revert to the default service.
After you create a database, the instance is left running, and the database is open and available for normal database use. You may want to perform other actions, some of which are discussed in this section.
Note Regarding Security Enhancements:In this release of Oracle Database and in subsequent releases, several enhancements are being made to ensure the security of default database user accounts. You can find a security checklist for this release in Oracle Database Security Guide. Oracle recommends that you read this checklist and configure your database accordingly.
Once the database is created, you can configure it to take advantage of Oracle Identity Management. For information on how to do this, please refer to Oracle Advanced Security Administrator's Guide.
Caution:To prevent unauthorized access and protect the integrity of your database, it is important that new passwords for user accounts
Additional administrative accounts are provided by Oracle Database that should be used only by authorized users. To protect these accounts from being used by unauthorized users familiar with their Oracle-supplied passwords, these accounts are initially locked with their passwords expired. As the database administrator, you are responsible for the unlocking and resetting of these accounts.
Table 2-5 lists the administrative accounts that are provided by Oracle Database. Not all accounts may be present on your system, depending upon the options that you selected for your database.
Table 2-5 Administrative User Accounts Provided by Oracle Database
||The Oracle Text account||Oracle Text Reference|
||The account used by the Management Agent component of Oracle Enterprise Manager to monitor and manage the database||Oracle Enterprise Manager Grid Control Installation and Basic Configuration|
||The Oracle Label Security administrator account||Oracle Label Security Administrator's Guide|
||The schema used by Oracle Spatial for storing Geocoder and router data||Oracle Spatial User's Guide and Reference|
||The Oracle Spatial and Oracle interMedia Locator administrator account||Oracle Spatial User's Guide and Reference|
||The Oracle Data Mining account.||Oracle Data Mining Administrator's Guide
||The account used to create OLAP metadata structures. It owns the OLAP Catalog (CWMLite).||Oracle OLAP Application Developer's Guide|
||The Oracle interMedia user. Plug-ins supplied by Oracle and third party format plug-ins are installed in this schema.||Oracle interMedia User's Guide|
||The Oracle interMedia administrator account||Oracle interMedia User's Guide|
||The account that supports plan stability. Plan stability enables you to maintain the same execution plans for the same SQL statements. OUTLN acts as a role to centrally manage metadata associated with stored outlines.||Oracle Database Performance Tuning Guide|
||The account that stores the information views for the SQL/MM Still Image Standard||Oracle interMedia User's Guide|
||The account used to perform database administration tasks||Oracle Database Administrator's Guide|
||The account used to perform Oracle Enterprise Manager database administration tasks. Note that SYS and SYSTEM can also perform these tasks.||Oracle Enterprise Manager Grid Control Installation and Basic Configuration|
||Another account used to perform database administration tasks.||Oracle Database Administrator's Guide|
The Oracle Database distribution media can includes various SQL files that let you experiment with the system, learn SQL, or create additional tables, views, or synonyms.
Oracle Database includes sample schemas that help you to become familiar with Oracle Database functionality. All Oracle Database documentation and training materials are being converted to the Sample Schemas environment as those materials are updated.
The Sample Schemas can be installed automatically by the Database Configuration Assistant, or you can install them manually. The schemas and installation instructions are described in detail in Oracle Database Sample Schemas.
In addition to the views listed previously in "Viewing Parameter Settings", you can view information about your database content and structure using the following views:
||Displays permanent database properties|
||Displays the global database name|
||Contains database information from the control file|