Release 1 (9.0.1)
Part Number A90117-01
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| Oracle9i Database Administrator's Guide Release 1 (9.0.1) Part Number A90117-01 |
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This chapter discusses the process of creating an Oracle database, and contains the following topics:
See Also:
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. Creating a database can also 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. The following are some recommended actions:
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Part II, "Oracle Server Processes and Storage Structure" Part III, "Schema Objects" |
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Oracle9i Database Performance Guide and Reference Your Oracle operating system specific documentation |
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"Initialization Parameters and Database Creation" |
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Chapter 7, "Managing the Online Redo Log" Chapter 8, "Managing Archived Redo Logs" |
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To create a new database, the following prerequisites must be met:
All of these are discussed in the Oracle installation guide specific to your operating system. Additionally, the Oracle Universal Installer will guide you through your installation and provide help in setting up environment variables, directory structure, and authorizations.
Creating a database includes the following operations:
You use the CREATE DATABASE statement to perform these operations, but other actions are necessary before you have an operational database. A few of these actions are creating users and temporary tablespaces, building views of the data dictionary tables, and installing Oracle built-in packages. This is why the database creation process involves executing prepared scripts. But, you do not necessarily have to prepare this script yourself.
You have the following options for creating your new Oracle database:
The Database Configuration Assistant 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 chose not to use the Database Configuration Assistant, or you can launch it as a standalone tool at any time in the future to create a database. See "The Oracle Database Configuration Assistant".
If you already have existing scripts for creating your database, you can still create your database manually. However, consider editing your existing script to take advantage of new Oracle features. Oracle provides a sample database creation script and a sample initialization parameter file with the database software files it distributes, both of which can be edited to suit your needs. See "Manually Creating an Oracle Database".
If you are using a previous release of Oracle, database creation is required only if you want an entirely new database. Otherwise, you can migrate or upgrade your existing Oracle database managed by a previous version or release of Oracle and use it with the new version of the Oracle software. Database migration and upgrade are not discussed in this book. The Oracle9i Database Migration manual contains information about migrating an existing database.
The Oracle Database Configuration Assistant (DBCA) is a graphical user interface (GUI) tool that interacts with the Oracle Universal Installer, or can be used standalone, to simplify the creation of a database. Online help is available to assist you in its use.
You can create or delete a database using the Database Configuration Assistant. You can configure database options so as to add options that have not been previously configured. Additionally, the Database Configuration Assistant enables you to create and manage database templates. You can create a template of a database definition and later modify that template, or you can modify templates supplied by Oracle. You can also create a template of an existing database and clone it.
The Oracle Database Configuration Assistant can be used to create single instance databases, or it can be used to create or add instances in an Oracle Real Application Clusters environment.
This section contains the following topics that introduce you to the Oracle Database Configuration Assistant:
These are a few of the advantages of using the Oracle Database Configuration Assistant:
You can create a database from predefined templates provided by Oracle or from templates that you or others have created. When you select a template, you can choose either to include datafiles or not. If you select a template with datafiles, you will be able to save the database creation information as a template or script. You can run the script later to create a new database.
This section does not discuss all of the choices available to you when you use the Oracle Database Creation Assistant to create a database. Rather, it is intended to provide an introduction to its use. Wizards will guide you in making choices for defining the database that you want to create.
Oracle provides templates for the following environments:
You have the option of viewing details for a template. The "show details" page displays specific information about the database defined by a template including:
You can save the details page as an HTML file.
When you select a template, you also specify whether the database definition is to include datafiles. The following types of databases are created accordingly:
You are guided thorough a series of pages that allow you to further define your database or to accept default parameter values and file locations as recommended by Oracle. You provide a global database name, specify database options to include, determine mode (dedicated server of shared server), and ultimately you can specify initialization parameter.
When specifying initialization parameters, the first page presented is the "memory parameters" page. It is used to determine the values of initialization parameters that size the initial System Global Area (SGA). You select one of the following options:
After you have completed the specification of the parameters that define your database you can:
Select to create the database now. For more information on the creation parameters, refer to the summary dialog that appears when you start the database creation process.
Select to save the database creation parameters as a template. This template will be automatically added to the list of available database creation templates.
Select to generate the scripts used to create the database. The scripts are generated from the database parameters you specified in the previous pages. You can use the scripts as a checklist, or to create the database later without using the Database Creation Assistant.
When you elect to configure database options, you can add Oracle options that have not previously been configured for use with your database
The following is a partial list of Oracle options or functionality that you can install in your database. Oracle provides a complete list from which you can select on the "configure database options" page. Some of the listed options might already be installed depending upon how you defined the database. Those options that are already installed are noted as such (grayed out).
The Oracle Database Configuration Assistant enables you to delete a database. When you do so, you delete the database instance and its control file(s), redo log files, and data files. The initialization parameter file is not deleted.
A template is a definition of a database. Oracle provides some basic templates for you to use, as discussed earlier in "Creating a Database", or you have the option of saving database definitions that you create yourself. These saved definitions can then be used to create new databases in the future, without having to completely redefine them. Oracle saves templates in XML files.
The following are some of the advantages of using templates:
A "template management" page provides you with several options that enable you to modify existing definitions or to create definitions based upon existing databases:
From an existing template, create a new template based on the pre-defined template settings. You can add or change any template settings such as initialization parameters, storage parameters, or use custom scripts.
From an existing database (structure only), create a new template whose structure is identical to the existing database. This includes tablespaces and storage. You can use an existing database that is either local or remote.
From an existing database (structure as well as data) create a template that has both the structure and data of an existing database. You can only use an existing database that is local.
You can view the "show details" page to see detail information about the templates you create or modify.
The "template management" page also allows you to delete existing templates.
This section presents the steps involved when you create a database manually. These steps should be followed in the order presented. You will previously have created your environment for creating your Oracle database, including most operating system dependent environmental variables, as part of the Oracle software installation process.
Step 1: Decide on Your Instance Identifier (SID)
Step 2: Establish the Database Administrator Authentication Method
Step 3: Create the Initialization Parameter File
Step 4: Connect to the Instance
Step 6: Issue the CREATE DATABASE Statement
Step 7: Create Additional Tablespaces
Step 8: Run Scripts to Build Data Dictionary Views
Step 9: Run Scripts to Install Additional Options (Optional)
Step 10: Create a Server Parameter File (Recommended)
The examples shown in these steps are to create the database mynewdb.
Decide on a unique Oracle system identifier (SID) for your instance and set the ORACLE_SID environment variable accordingly. This identifier is used to avoid confusion with other Oracle 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 (System Global Area and background processes) for any Oracle database is started using an initialization parameter file. One way of getting started on your 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 ease of operation, store your initialization parameter file in Oracle's default location, using the default name. That way, when you start your database, it is not necessary to specify the PFILE parameter because Oracle automatically looks in the default location for the initialization parameter file.
Default parameter file locations are shown in the following table:
The following is the initialization parameter file used to create the mynewdb database.
# Cache and I/O DB_BLOCK_SIZE=4096 DB_CACHE_SIZE=20971520 # Cursors and Library Cache CURSOR_SHARING=SIMILAR OPEN_CURSORS=300 # Diagnostics and Statistics BACKGROUND_DUMP_DEST=/vobs/oracle/admin/mynewdb/bdump CORE_DUMP_DEST=/vobs/oracle/admin/mynewdb/cdump TIMED_STATISTICS=TRUE USER_DUMP_DEST=/vobs/oracle/admin/mynewdb/udump # Control File Configuration CONTROL_FILES=("/vobs/oracle/oradata/mynewdb/control01.ctl", "/vobs/oracle/oradata/mynewdb/control02.ctl", "/vobs/oracle/oradata/mynewdb/control03.ctl") # Archive LOG_ARCHIVE_DEST_1='LOCATION=/vobs/oracle/oradata/mynewdb/archive' LOG_ARCHIVE_FORMAT=%t_%s.dbf LOG_ARCHIVE_START=TRUE # Shared Server # Uncomment and use first DISPATCHES parameter below when your listener is # configured for SSL # (listener.ora and sqlnet.ora) # DISPATCHERS = "(PROTOCOL=TCPS)(SER=MODOSE)", # "(PROTOCOL=TCPS)(PRE=oracle.aurora.server.SGiopServer)" DISPATCHERS="(PROTOCOL=TCP)(SER=MODOSE)", "(PROTOCOL=TCP)(PRE=oracle.aurora.server.SGiopServer)", (PROTOCOL=TCP) # Miscellaneous COMPATIBLE=9.0.0 DB_NAME=mynewdb # Distributed, Replication and Snapshot DB_DOMAIN=us.oracle.com REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE # Network Registration INSTANCE_NAME=mynewdb # Pools JAVA_POOL_SIZE=31457280 LARGE_POOL_SIZE=1048576 SHARED_POOL_SIZE=52428800 # Processes and Sessions PROCESSES=150 # Redo Log and Recovery FAST_START_MTTR_TARGET=300 # Resource Manager RESOURCE_MANAGER_PLAN=SYSTEM_PLAN # Sort, Hash Joins, Bitmap Indexes SORT_AREA_SIZE=524288 # System Managed Undo and Rollback Segments UNDO_MANAGEMENT=AUTO UNDO_TABLESPACE=undotbs
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$ SQLPLUS /nolog CONNECT SYS/password AS SYSDBA
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 option. In this example, because the initialization parameter file is stored in the default location, you are not required to specify the PFILE clause:
STARTUP NOMOUNT
At this point, there is no database. Only the SGA is created and background processes are started in preparation for the creation of a new database.
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To create the new database, use the CREATE DATABASE statement. When you execute a CREATE DATABASE statement, Oracle performs (at least) the following operations. Other operations are performed depending upon the clauses that you specify in the CREATE DATABASE statement or initialization parameters that you have set.
ARCHIVELOG mode.
SYSTEM tablespace and the SYSTEM rollback segment
The following statement creates database mynewdb:
CREATE DATABASE mynewdb MAXINSTANCES 1 MAXLOGHISTORY 1 MAXLOGFILES 5 MAXLOGMEMBERS 5 MAXDATAFILES 100 DATAFILE '/vobs/oracle/oradata/mynewdb/system01.dbf' SIZE 325M REUSE UNDO TABLESPACE undotbs DATAFILE '/vobs/oracle/oradata/mynewdb/undotbs01.dbf' SIZE 200M REUSE AUTOEXTEND ON NEXT 5120K MAXSIZE UNLIMITED DEFAULT TEMPORARY TABLESPACE tempts1 CHARACTER SET US7ASCII NATIONAL CHARACTER SET AL16UTF16 LOGFILE GROUP 1 ('/vobs/oracle/oradata/mynewdb/redo01.log') SIZE 100M, GROUP 2 ('/vobs/oracle/oradata/mynewdb/redo02.log') SIZE 100M, GROUP 3 ('/vobs/oracle/oradata/mynewdb/redo03.log') SIZE 100M;
A database is created with the following characteristics:
mynewdb. Its global database name is mynewdb.us.oracle.com. See "DB_NAME Initialization Parameter" and "DB_DOMAIN Initialization Parameter".
CONTROL_FILES initialization parameter. See "Specifying Control Files".
MAXINSTANCES specified that only one instance can have this database mounted and open.
MAXDATAFILES specifies the maximum number of datafiles that can be open in the database. This number affects the initial sizing of the control file.
You can set several limits during database creation. Some of these limits are also subject to superseding limits of the operating system and can be affected by them. For example, if you set
For more information about setting limits during database creation, see the Oracle9i SQL Reference and your operating system specific Oracle documentation.
Note:
MAXDATAFILES, Oracle allocates enough space in the control file to store MAXDATAFILES filenames, even if the database has only one datafile initially. However, because the maximum control file size is limited and operating system dependent, you might not be able to set all CREATE DATABASE parameters at their theoretical maximums.
SYSTEM tablespace, consisting of the operating system file /vobs/oracle/oradata/mynewdb/system01.dbf is created as specified by the DATAFILE clause. If the file already exists, it is overwritten.
UNDO_TABLESPACE clause creates and names the undo tablespace to be used to store undo records for this database. See Chapter 13, "Managing Undo Space".
DEFAULT_TEMPORARY_TABLESPACE clause creates and names a default temporary tablespace for this database. See "Creating a Default Temporary Tablespace".
US7ASCII character set is used to store data in this database.
AL16UTF16 character set is specified as the NATIONAL CHARACRTER SET used to store data in columns of specifically defined as NCHAR, NCLOB, or NVARCHAR2.
LOGFILE clause. MAXLOGHISTORY, MAXLOGFILES, and MAXLOGMEMBERS define limits for the redo log. See Chapter 7, "Managing the Online Redo Log".
ARCHIVELOG clause is not specified in this CREATE DATABASE statement, redo log files will not initially be archived. This is customary during database creation and an ALTER DATABASE statement can be used later to switch to ARCHIVELOG mode. The initialization parameters in the initialization parameter file for mynewdb affecting archiving are LOG_ARCHIVE_DEST_1, LOG_ARCHIVE_FORMAT, and LOG_ARCHIVE_START. See Chapter 8, "Managing Archived Redo Logs".
SET TIME_ZONE clause of the CREATE DATABASE statement. If omitted (as it is in this case), 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. For information about the time zone files used by Oracle to obtain time zone data, see "Setting and Managing the Time Zone".
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Oracle9i SQL Reference for more information about specifying the clauses and parameter values for the |
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 '/vobs/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 '/vobs/oracle/oradata/mynewdb/indx01.dbf' SIZE 25M REUSE AUTOEXTEND ON NEXT 1280K MAXSIZE UNLIMITED EXTENT MANAGEMENT LOCAL; EXIT
For information about creating tablespaces, see Chapter 11, "Managing Tablespaces".
Run the scripts necessary to build views, synonyms, and PL/SQL packages:
CONNECT SYS/password AS SYSDBA
@/vobs/oracle/rdbms/admin/catalog.sql;
@/vobs/oracle/rdbms/admin/catproc.sql;
EXIT
The following table contains descriptions of the scripts:
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 Oracle9i Database Reference.
See your Oracle installation guide for your operating system for the location of these scripts.
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's data dictionary.
See your Oracle documentation for the specific products that you plan to install for installation and administration instructions.
Oracle recommends 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 instance is shut down, then restarted using the server parameter file (in the default location).
CONNECT SYS/passwordAS SYSDBA -- create the server parameter file CREATE SPFILE='/vobs/oracle/dbs/spfilemynewdb.ora' FROM PFILE='/vobs/oracle/admin/mynewdb/scripts/init.ora'; SHUTDOWN -- this time you will start up using the server parameter file CONNECT SYS/passwordAS SYSDBA STARTUP EXIT
You should make 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 the Oracle9i Backup and Recovery Concepts.
In addition to using the Database Configuration Assistant for creating your database, Oracle9i offers you other options that can simplify the creation, operation, and management of your database. There are clauses, some shown in the above CREATE DATABASE statement, which are discussed in this section. Additionally, you can choose to use the Oracle Managed Files feature, which automatically creates and manages the underlying operating system files of your database.
Also discussed in this section is the management of the time zone files used to support the SET TIME_ZONE feature.
This section contains the following topics:
Optionally, instead of using rollback segments in your database, you can use an undo tablespace. This requires the use of a different set of initialization parameters and, if creating the database for the first time, the UNDO TABLESPACE clause of the CREATE DATABASE statement. You also must include the following initialization parameter:
UNDO_MANAGEMENT=AUTO
This initialization parameter tells Oracle that you want to operate your database automatic undo management mode. In this mode rollback information, referred to as undo, is stored in an undo tablespace rather than rollback segments and is managed by Oracle.
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Chapter 13, "Managing Undo Space" for information about the creation and use of undo tablespaces |
The DEFAULT TEMPORARY TABLESPACE clause of the CREATE DATABASE statement specifies that a temporary tablespace is to be created at database creation time. This tablespace is used as the default temporary tablespace for users who are not otherwise assigned a temporary tablespace.
Users can be explicitly assigned a default temporary tablespace in the CREATE USER statement. But, if no temporary tablespace is specified, they default to using the SYSTEM tablespace. It is not good practice to store temporary data in the SYSTEM tablespace. To avoid this problem, and to avoid the need to assign every user a default temporary tablespace at CREATE USER time, you can use the DEFAULT TEMPORARY TABLESPACE clause of CREATE DATABASE.
If you decide later to change the default temporary tablespace, or to create an initial one after database creation, you can do so. You do this by creating a new temporary tablespace (CREATE TEMPORARY TABLESPACE), 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 temporary default tablespace.
The following statement assigns a new default temporary tablespace:
ALTER TABLESPACE DEFAULT TEMPORARY TABLESPACE tempts2
The new default temporary tablespace must be an existing temporary tablespace.
You cannot drop a default temporary tablespace, but you can assign a new default temporary tablespace, then drop the former one. You are not allowed to change a default temporary tablespace to a permanent tablespace, nor can you take a default temporary tablespace offline.
Users can obtain the name of the current default temporary tablespace using the DATABASE_PROPERTIES view. The PROPERTY_NAME column contains the value "DEFAULT_TEMP_TABLESPACE" and the PROPERTY_VALUE column contains the default temporary tablespace name.
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If you include the DB_CREATE_FILE_DEST or DB_CREATE_ONLINE_LOG_DEST_n initialization parameters in your initialization parameter file, you enable Oracle to create and manage the underlying operating system files of your database. Oracle will automatically create and manage the operating system files for the following database structures, dependent upon the initialization parameters you specify and how you specify clauses in your CREATE DATABASE statement:
Briefly, this is how the Oracle Managed Files feature works with the CREATE DATABASE statement presented earlier in this section and repeated here.
CREATE DATABASE rbdb1 UNDO TABLESPACE undotbs DEFAULT TEMPORARY TABLESPACE tempts1;
DATAFILE clause is specified, therefore Oracle creates an Oracle-managed datafile for the SYSTEM tablespace.
LOGFILE clauses are included, therefore Oracle creates two online redo log file groups that are Oracle managed.
DATAFILE subclause is specified for the UNDO TABLESPACE clause, therefore Oracle creates an Oracle-managed datafile for the undo tablespace.
TEMPFILE subclause is specified for the DEFAULT TEMPORARY TABLESPACE clause, therefore Oracle creates an Oracle-managed tempfile.
CONTROL_FILES initialization parameter is specified in the initialization parameter file, Oracle creates an Oracle-managed control file.
Oracle9i enables you to set the time zone for your database using the SET TIME_ZONE clause of the CREATE DATABASE statement. This section provides information on the time zone files used to support this feature, specifically on Solaris platforms. Names of directories, filenames, and environment variables may differ for each platform but will probably be the same for all UNIX platforms.
The time zone files contain the valid time zone names and the following information is included for each zone (note that abbreviations are only used in conjunction with the zone names):
There are 2 time zone files under the Oracle installation directory:
$ORACLE_HOME/oracore/zoneinfo/timezone.dat
This is the default. It contains the most commonly used time zones and is smaller, thus enabling better database performance.
$ORACLE_HOME/oracore/zoneinfo/timezlrg.dat
This file contains the larger set of defined time zones and should be used by users who require zones that are not defined in the default timezone.dat file. Note that this larger set of zone information may affect performance.
To enable the use of the larger time zone data file, the DBA must do the following:
ORA_TZFILE to the full pathname of the location for the timezlrg.dat file.
Once the larger timezlrg.dat is used, it must continue to be used unless the user is sure that none of the nondefault zones are used for data that is stored in the database. Also, all databases that share information must use the same time zone data file.
To view the time zone names, use the following query:
SELECT * FROM V$TIMEZONE_NAMES
If for any reason database creation fails, shut down the instance and delete any files created by the CREATE DATABASE statement before you attempt to create it once again. After correcting the error that caused the failure of the database creation, try running the script again.
To drop a database, you must remove its datafiles, redo log files, and all other associated files (control files, initialization parameter files, archived log files). To view the names of the database's datafiles, redo log files, and control files, query the data dictionary views V$DATAFILE, V$LOGFILE, and V$CONTROLFILE, respectively.
If the database is in archive log mode, locate the archive log destinations by inspecting the initialization parameters LOG_ARCHIVE_DEST_n, or LOG_ARCHIVE_DEST and LOG_ARCHIVE_DUPLEX_DEST.
If you used the Database Configuration Assistant to create your database, you can use that tool to delete your database and clean up the files.
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See Also:
Oracle9i Database Reference for more information about these views and initialization parameters |
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.
A newly created database has least three users that are useful for administering your database: SYS, SYSTEM and OUTLN (owner of schema where stored outlines are stored).
Depending on the features and options installed, other users can also be present. Some of these users are:
MDSYS (interMedia Spatial)
ORDSYS (interMedia Audio)
ORDPLUGINS (interMedia Audio)
CTXSYS (Oracle Text)
DBSNMP (Enterprise Manager Intelligent Agent)
To change the password for user DBSNMP refer to Oracle Intelligent Agent User's Guide.
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The Oracle server distribution media can include various SQL files that let you experiment with the system, learn SQL, or create additional tables, views, or synonyms.
Starting with Oracle9i, Oracle provides sample schemas that enable you to become familiar with Oracle functionality. Some Oracle documents and books use these sample schemas for presenting examples. There is an ongoing effort for most Oracle books to convert to the use of Sample Schemas based examples.
The following table briefly describes the sample schemas:
Sample Schemas can be installed automatically for you by the Oracle Database Configuration Assistant or you can install it manually. The schemas and installation instructions are described in detail in Oracle9i Sample Schemas.
Oracle has attempted to provide appropriate values in the starter initialization parameter file provided with your database software. 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, Oracle supplies defaults.
If you are creating an Oracle database for the first time, it is suggested 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 for the current instance with the ALTER SYSTEM statement. Later, you can choose to permanently add or change parameter values by updating them manually in the traditional text initialization parameter file. Or, you can create a binary server parameter file that enables you to use the ALTER SYSTEM statement to make initialization parameter changes that can persist across shutdown and startup. Both of these options are discussed in "Managing Initialization Parameters Using a Server Parameter File".
This section discusses some of the initialization parameters you may choose to add or edit before you create your new database.
The following topics are contained in this section:
Oracle9i Database Reference for descriptions of all initialization parameters including their default settings
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A database's global database name consists of the local database name that you assign and its location within a network structure. The DB_NAME initialization parameter determines the local name component of the database's name, while 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, but you must also shut down and restart the database after changing the DB_NAME and DB_DOMAIN initialization parameters and re-creating the control file.
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, pay special attention to this initialization parameter before database creation.
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Part VI, "Distributed Database Management" for more information about distributed databases |
Include the CONTROL_FILES initialization parameter in your new parameter file and set its value to a list of control filenames to use for the new database. When you execute the CREATE DATABASE statement, the control files listed in the CONTROL_FILES parameter will be created. If no filenames are listed for the CONTROL_FILES parameter, Oracle uses a default operating system dependent filename.
If you want Oracle to create new operating system files when creating your database's control files, the filenames listed in the CONTROL_FILES parameter must not match any filenames that currently exist on your system. If you want Oracle to reuse or overwrite existing files when creating your database's control files, ensure that the filenames listed in the CONTROL_FILES parameter match the filenames that are to be reused.
Oracle Corporation strongly recommends you use at least two control files stored on separate physical disk drives for each database.
The 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 can support up to 4 additional non-standard 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 not specified, the default data block size is operating system specific, and is generally adequate.
The block size cannot be changed after database creation, except by re-creating the database. If a database's block size is different from the operating system block size, make the database block size a multiple of the operating system's block size.
For example, if your operating system's block size is 2K (2048 bytes), the following setting for the DB_BLOCK_SIZE initialization parameter is valid:
DB_BLOCK_SIZE=4096
In some cases, you may want to specify a block size larger than your operating system block size. A larger data block size provides greater efficiency in disk and memory I/O (access and storage of data). Such cases include the following scenarios:
Tablespaces of non-standard block sizes can be created using the CREATE TABLESPACE statement and specifying the BLOCKSIZE clause. These non-standard block sizes can have any power-of-two value between 2K and 32K: specifically, 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 non-standard block sizes, you must configure sub-caches within the buffer cache area of the SGA memory for all of the non-standard block sizes that you intend to use. The initialization parameters used for configuring these sub-caches are described in the next section, "Setting Initialization Parameters that Affect the Size of the 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 datawarehouse environment that uses a standard block size of 8K.
The initialization parameters discussed in this section affect the amount of memory that is allocated to the System Global Area. Except for the SGA_MAX_SIZE initialization parameter, they are dynamic parameters which 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.
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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 DB_nK_CACHE_SIZE parameter set. Oracle assigns an appropriate default value to the DB_CACHE_SIZE parameter, but the DB_nK_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.
The DB_CACHE_SIZE initialization parameter replaces the DB_BLOCK_BUFFERS initialization parameter that was used in previous releases. The DB_CACHE_SIZE parameter specifies the size of the cache of standard block size buffers, where the standard block size is specified by DB_BLOCK_SIZE.
For backward compatibility the DB_BLOCK_BUFFERS parameter will still work, but it remains a static parameter and cannot be combined with any of the dynamic sizing parameters.
The sizes and numbers of non-standard 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 the above example, the parameters specify that the standard block size of the database will be 4K. The size of the cache of standard block size buffers will be 12M. Additionally, 2K and 8K caches will be configured with sizes of 8M and 4M respectively.
The SHARED_POOL_SIZE initialization parameter is a dynamic parameter (in previous releases it was not dynamic) that allows you to specify or adjust the size of the shared pool component of the SGA. Oracle selects an appropriate default value.
The LARGE_POOL_SIZE initialization parameter is a dynamic parameter (in previous releases it was not dynamic) that allows you to specify or adjust the size of the large pool component of the SGA. Oracle selects an appropriate default value.
The 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, and large 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 SGA_MAX_SIZE.
If you do not specify SGA_MAX_SIZE, then Oracle selects a default value that is the sum of all components specified or defaulted at initialization time.
The PROCESSES initialization parameter determines the maximum number of operating system processes that can be connected to Oracle concurrently. The value of this parameter must be 6 or greater (5 for the background processes plus 1 for each user process). For example, if you plan to have 50 concurrent users, set this parameter to at least 55.
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. Oracle refers to these records collectively as undo. Oracle allows you to store undo in an undo tablespace or in rollback segments.
The UNDO_MANAGEMENT initialization parameter determines whether an instance will start up in automatic undo management mode, where undo is stored in an undo tablespace, or rollback segment undo mode, where undo is stored in rollback segments. A value of AUTO enables automatic undo management mode, MANUAL enables rollback segment undo mode. For backward compatibility, the default is MANUAL.
When the instance starts up in automatic undo management mode, it selects the first available undo tablespace in the instance for storing undo. A default undo tablespace named SYS_UNDOTBS is automatically created when you execute a CREATE DATABASE statement and the UNDO_MANAGEMENT initialization parameter is set to AUTO. This is the undo tablespace that Oracle will normally select whenever you start up the database.
Optionally, you can specify the UNDO_TABLESPACE initialization parameter. This causes the instance to use the undo tablespace specified by the parameter. The UNDO_TABLESPACE parameter can be used to assign a specific undo tablespace to an instance in an Oracle Real Application Clusters environment.
If there is no undo tablespace available, the instance will start, but uses the SYSTEM rollback segment. This 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.
Oracle recommends using an undo tablespace rather than rollback segments. An undo tablespace is easier to administer and enables you to explicitly set an undo retention time.
The ROLLBACK_SEGMENTS parameter is a list of the non-system rollback segments an Oracle instance acquires at database startup if the database is to operate in rollback segment undo mode. List your rollback segments as the value of this parameter. If no rollback segments are specified, the system rollback segment is used.
The ROLLBACK_SEGMENTS initialization parameter is supported for backward compatibility. Oracle recommends using an undo tablespace rather than rollback segments.
Oracle helps you ensure that your site complies with its Oracle license agreement. If your site is licensed by concurrent usage, you can track and limit the number of sessions concurrently connected to an instance. If your site is licensed by named users, you can limit the number of named users created in a database. To use this facility, you need to know which type of licensing agreement your site has and what the maximum number of sessions or named users is. Your site might use either type of licensing (session licensing or named user licensing), but not both.
The licenses initialization parameters are introduced here, but are discussed in greater detail in "Session and User Licensing".
You can set a limit on the number of concurrent sessions that can connect to a database. To set the maximum number of concurrent sessions for an instance, set the initialization parameter LICENSE_MAX_SESSIONS in the initialization parameter file that starts the instance, as shown in the following example:
LICENSE_MAX_SESSIONS = 80
In addition to setting a maximum number of sessions, you can set a warning limit on the number of concurrent sessions. Once this limit is reached, additional users can continue to connect (up to the maximum limit), but Oracle sends a warning to each connecting user. To set the warning limit for an instance, set the parameter LICENSE_SESSIONS_WARNING. Set the warning limit to a value lower than LICENSE_MAX_SESSIONS.
For running with Oracle Real Application Cluster instances, each instance can have its own concurrent usage limit and warning limit. However, the sum of the instances' limits must not exceed the site's session license.
You can set a limit on the number of users created in the database. Once this limit is reached, you cannot create more users.
To limit the number of users created in a database, set the LICENSE_MAX_USERS initialization parameter in the database's initialization parameter file, as shown in the following example:
LICENSE_MAX_USERS = 200
For Oracle Real Application Cluster instances, all instances connected to the same database should have the same named user limit.
Oracle has traditionally stored initialization parameters in a text initialization parameter file. Starting with Oracle9i, you can choose to maintain initialization parameters in a binary server parameter file.
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 where the Oracle database server executes. 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 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 browsed or edited using a text editor. Oracle provides other interfaces for viewing and modifying parameter settings.
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 choose to use the traditional text initialization parameter file, you must specify the PFILE clause when issuing the STARTUP command. Explicit 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 you are using Oracle9i Real Application Clusters, 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 Oracle Real Application Cluster instances, are discussed in:
Note:
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.
The server parameter file must initially be 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 spfile$ORACLE_SID.ora.
CREATE SPFILE FROM PFILE='/u01/oracle/dbs/init.ora';
Another example, below, 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';
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.
When the server parameter file is created from the 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 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 recreate the same server parameter file that is currently being used by the instance.
The 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.
The 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:
SPFILE parameter to specify the name of a server parameter file to use at instance startup
The ALTER SYSTEM statement allows you to set, change, or delete (restore to default value) initialization parameter values. When the ALTER SYSTEM statement is used to alter a parameter setting in a traditional initialization parameter file, the change affects only the current instance, since there is no mechanism for automatically updating initialization parameters on disk. They must be manually updated in order to be passed to a future instance. Using a server parameter file overcomes this limitation.
Use the SET clause of the ALTER SYSTEM statement to set or change initialization parameter values. Additionally, the SCOPE clause specifies the scope of a change as described in the following table:
It is an error to specify SCOPE=SPFILE or 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.
A COMMENT clause allows a comment string to be associated with the parameter update. When you specify SCOPE as SPFILE or 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 also specifies 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;
Another example illustrates setting a complex initialization parameter that takes a list of strings. Specifically, the parameter value being set is the LOG_ARCHIVE_DEST_n initialization parameter. The case could be that either the parameter is being changed to a new value or a new archive destination is being added.
ALTER SYSTEM SET LOG_ARCHIVE_DEST_4='LOCATION=/u02/oracle/rbdb1/',MANDATORY,'REOPEN=2' COMMENT='Add new destimation on Nov 29' SCOPE=SPFILE;
Note that when a value consists of a list of strings, the syntax of the ALTER SYSTEM SET statement does not support editing each element of the list of values 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.
For initialization parameters whose values are string values you can restore a parameter to its default value (effectively deleting it), by using the following syntax:
ALTER SYSTEM SET parameter = '';
For numeric and boolean value parameters, you must specifically set the parameter back to its original default value.
You can export a server parameter file to create a traditional text initialization parameter file. Reasons for doing this include:
SHOW PARAMETERS command or selecting from the V$PARAMETER or V$PARAMETER2 views.
The exported file can also be used to start up an instance using the PFILE option.
The CREATE PFILE statement is used to export a server parameter file. You must have the SYSDBA or the SYSOPER system privilege to execute this 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, a platform-specific name is used for the initialization parameter file, 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 where the names of the files are specified:
CREATE PFILE='/u01/oracle/dbs/test_init.ora' FROM SPFILE='/u01/oracle/dbs/test_spfile.ora';
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 have the following options:
You have several options for viewing parameter settings.
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