Oracle7 Server Administrator's Guide
Parameters
As described in Step 3 of "Creating an Oracle7 Database", Oracle suggests you alter a minimum set of parameters. These parameters are described in the following sections:
DB_NAME and DB_DOMAIN
A database's global database name (name and location within a network structure) is created by setting both the DB_NAME and DB_DOMAIN parameters before database creation. After creation, the database's name cannot be easily changed. The DB_NAME 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 should 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
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 (of 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.
See Also: For more information about distributed databases, see Oracle7 Server Distributed Systems, Volume I.
CONTROL_FILES
Include the CONTROL_FILES parameter in your new parameter file and set its value to a list of control filenames to use for the new database. If you want Oracle7 to create new operating system files when creating your database's control files, make sure that the filenames listed in the CONTROL_FILES parameter do not match any filenames that currently exist on your system. If you want Oracle7 to reuse or overwrite existing files when creating your database's control files, make sure that the filenames listed in the CONTROL_FILES parameter match the filenames that currently exist.
Warning: Use extreme caution when setting this option. If you inadvertently specify a file that you did not intend and execute the CREATE DATABASE statement, the previous contents of that file will be overwritten.
If no filenames are listed for the CONTROL_FILES parameter, Oracle7 uses a default filename.
Oracle Corporation strongly recommends you use at least two control files stored on separate physical disk drives for each database. Therefore, when specifying the CONTROL_FILES parameter of the new parameter file, follow these guidelines:
- List at least two filenames for the CONTROL_FILES parameter.
- Place each control file on a separate physical disk drives by fully specifying filenames that refer to different disk drives for each filename.
Note: The file specification for control files is operating system-dependent. Regardless of your operating system, always fully specify filenames for your control files.
When you execute the CREATE DATABASE statement (in Step 7), the control files listed in the CONTROL_FILES parameter of the parameter file will be created.
See Also: The default filename for the CONTROL_FILES parameter is operating system-dependent. See your operating system-specific Oracle documentation for details.
DB_BLOCK_SIZE
The default data block size for every Oracle7 Server is operating system-specific. The Oracle7 data block size is typically either 2K or 4K. Generally, the default data block size is adequate. In some cases, however, a larger data block size provides greater efficiency in disk and memory I/O (access and storage of data). Such cases include:
- Oracle7 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 Oracle7 uses a small operating system block size. For example, if the operating system block size is 1K and the data block size matches this, Oracle7 may be performing an excessive amount of disk I/O during normal operation. To correct for this, all databases created should have a data block size that is larger than the operating system block size.
Each database's block size is set during database creation by the initialization parameter DB_BLOCK_SIZE. 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 data 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 would be valid:
DB_BLOCK_SIZE=4096
DB_BLOCK_SIZE also determines the size of the database buffers in the buffer cache of the System Global Area (SGA).
See Also: For details about your default block size, see your operating system-specific Oracle documentation.
DB_BLOCK_BUFFERS
This parameter determines the number of buffers in the buffer cache in the System Global Area (SGA). The number of buffers affects the performance of the cache. Larger cache sizes reduce the number of disk writes of modified data. However, a large cache may take up too much memory and induce memory paging or swapping.
Estimate the number of data blocks that your application accesses most frequently, including tables, indexes, and rollback segments. This estimate is a rough approximation of the minimum number of buffers the cache should have. Typically, 1000 or 2000 buffers is sufficient.
See Also: For more information about tuning the buffer cache, see the Oracle7 Server Tuning manual.
PROCESSES
This parameter determines the maximum number of operating system processes that can be connected to Oracle7 concurrently. The value of this parameter must include 5 for the background processes and 1 for each user process. For example, if you plan to have 50 concurrent users, set this parameter to at least 55.
ROLLBACK_
SEGMENTS
This parameter is a list of the rollback segments an Oracle7 instance acquires at database startup. List your rollback segments as the value of this parameter.
Attention: After installation, you must create at least one rollback segment in the SYSTEM tablespace in addition to the SYSTEM rollback segment before you can create any schema objects.
See Also: For more information about how many rollback segments you need, see Oracle7 Server Tuning.
License Parameters
Oracle7 helps you ensure that your site complies with its Oracle7 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.
See Also: For more information about managing licensing, see ![[*]](jump.gif)
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LICENSE_MAX_
SESSIONS and LICENSE_SESSIONS_
WARNING
You can set a limit on the number of concurrent sessions that can connect to a database on the specified computer. To set the maximum number of concurrent sessions for an instance, set the parameter LICENSE_MAX_SESSIONS in the 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 Oracle7 sends a warning for 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 instances running with the Parallel Server, 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.
See Also: For more information about setting these limits when using the Parallel Server, see Oracle7 Parallel Server Concepts & Administration.
LICENSE_MAX_
USERS
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 Oracle7 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 parameter in the database's parameter file, as shown in the following example:
LICENSE_MAX_USERS = 200
For instances running with the Parallel Server, all instances connected to the same database should have the same named user limit.
See Also: For more information about setting this limit when using the Parallel Server see the Oracle7 Parallel Server Concepts & Administration manual.