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Oracle® Database Platform Guide 10g Release 2 (10.2) for Microsoft Windows (32-Bit) Part Number B14304-03 |
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# 13 Oracle Database Specifications for Windows

Oracle Database for Windows uses initialization parameters to enable various features of the database every time an instance is started.

This chapter contains these topics:

- Initialization Parameter File Overview

- Sample File

- SGA_MAX_SIZE Parameter

- Initialization Parameters Without Windows-Specific Values

- Displaying Initialization Parameter Values

- Uneditable Database Initialization Parameters

- Calculating Database Limits

## Initialization Parameter File Overview

An initialization parameter file is an ASCII text file containing parameters. By changing parameters and values in an initialization parameter file, you can specify, for example:

- Amount of memory Oracle Database uses

- Whether to archive filled online redo logs

- Which control files currently exist

Every database instance has a corresponding initialization parameter file and an `ORACLE_SID` registry parameter that points to the system identifier for the instance.

The initialization parameter filename takes the form `init.ora`. A single instance might have several initialization parameter files, each having some differences that affect system performance.

Note: Your `init.ora` file for initialization parameters is set by Oracle Universal Installer during database installation. These parameter settings may vary depending on your hardware configuration. For descriptions of all initialization parameters and instructions for setting and displaying their values, see Oracle Database Reference.

### Location of the Initialization Parameter File

If you do not specify a different initialization file with option `PFILE` at database startup, then by default Oracle Database uses initialization parameter files located in

    ORACLE_HOME\Database\init.ora

Note: If you create a database manually using a SQL script, then you are required to create an initialization parameter file or copy an existing initialization parameter file and modify the contents. If you use Database Configuration Assistant to create a database, then the initialization parameter file is automatically created for you.

### Editing The Initialization Parameter File

To customize Oracle Database functions, you may be required to edit the initialization parameter file. Use only an ASCII text editor to modify the file.

### Database Configuration Assistant Renames init.ora

When you create a database using Database Configuration Assistant, a server parameter file (SPFILE) is created from the initialization parameter file, and the initialization parameter file is renamed. Oracle does not recognize the renamed file as an initialization parameter file, and it is not used after the instance is started.

If you want to modify an instance created with Database Configuration Assistant after it starts up, you must use `ALTER SYSTEM` statements. You cannot change the SPFILE itself, because it is a binary file that cannot be browsed or edited using a text editor. The location of the newly-created SPFILE is `ORACLE_BASE``\``ORACLE_HOME``\database`. The SPFILE filename is `spfile` `SID``.ora`.

See Also: "Managing Initialization Parameters Using a Server Parameter File" in Oracle Database Administrator's Guide

## Sample File

Oracle Database provides an annotated sample initialization parameter file with alternative values for initialization parameters. These values and annotations are preceded by comment signs (`#`), which prevent them from being processed. To activate a particular parameter, remove the preceding `#` sign. To de-activate a particular parameter, edit the initialization parameter file to add a comment sign. The sample file is called `initsmpl.ora`. and is located in

    ORACLE_BASE\ORACLE_HOME\admin\sample\pfile.

If you installed a starter database, the initialization parameter file used by the starter database is located in the same directory. You can use either `initsmpl.ora` or the starter database `init.ora` as a basis for creating a new Oracle Database initialization parameter file.

To use sample file `initsmpl.ora` as part of database creation:

1. Rename the sample file `init.ora`.

2. Edit this file to reflect the correct location of your database control files and the name of your database, as a minimum.

Here are two examples of activation and de-activation of alternative parameters. Several initialization parameters are specified with three different values to create a small, medium, or large System Global Area, respectively. The parameter that creates a small SGA is active in this first example:

    db_block_buffers = 200  # SMALL
    # db_block_buffers = 550  # MEDIUM
    # db_block_buffers = 3200 # LARGE

To create a medium-sized SGA, comment out the small parameter definition and activate the medium parameter definition. Edit the initialization parameter file as in this second example:

    # db_block_buffers = 200  # SMALL
      db_block_buffers = 550  # MEDIUM
    # db_block_buffers = 3200 # LARGE

## SGA_MAX_SIZE Parameter

Parameter `SGA_MAX_SIZE` holds the maximum size that System Global Area (SGA) can reach for a particular instance. Beginning with Oracle9i release 1 (9.0.1), Oracle Database can change its SGA configuration while the instance is running. This allows sizes of buffer cache, shared pool, and large pool to be changed without instance shutdown.

Oracle Database can start instances underconfigured and allow the instance to use more memory by growing SGA up to a maximum of `SGA_MAX_SIZE`. If no `SGA_MAX_SIZE` value is specified, then Oracle Database selects a default value that is the sum of all components specified or defaulted at initialization time. If `SGA_MAX_SIZE` specified in the initialization parameter file is less than the sum of all components specified or defaulted to at initialization time, then the setting of `SGA_MAX_SIZE` in the initialization parameter file serves as an upper bound.

See Also: Oracle Database Performance Tuning Guide for more information about SGA initialization parameters. Oracle Database Concepts for more information about SGA and its components

Memory allocated for the SGA of an instance is displayed on instance startup when using Oracle Enterprise Manager (or SQL*Plus). You can also display the SGA size of the current instance by using the SQL*Plus `SHOW` statement with the SGA clause.

## Initialization Parameters Without Windows-Specific Values

Oracle Database Reference describes default values for many initialization parameters as being operating system-specific. However, not all parameters that it describes as having operating system-specific values affect Windows. In these cases, Windows uses either the default value set in the Oracle Database kernel or does not use the parameter. Table 13-1 describes these initialization parameters:

Table 13-1 Initialization Parameters Without Windows-Specific Values

Parameter | Description
--- | ---
`AUDIT_FILE_DEST` | Not supported on Windows and should not be added to the initialization parameter file
`DB_WRITER_PROCESSES` | Supported, but typically unnecessary due to Windows asynchronous I/O capabilities
`COMPATIBLE_NO_RECOVERY` | Uses default value set in Oracle Database kernel (no Windows-specific value)
`BACKGROUND_CORE_DUMP` | Specifies whether Oracle Database includes SGA in core file for Oracle Database background processes
`SHADOW_CORE_DUMP` | Specifies whether Oracle Database includes SGA in core file for foreground (client) processes
`CORE_DUMP_DEST` | Specifies directory where Oracle Database dumps core files
`CPU_COUNT` | Oracle Database automatically sets value to number of processors available for your Oracle Database instance
`HI_SHARED_MEMORY_ADDRESS` | Not applicable to Windows
`SHARED_MEMORY_ADDRESS` | Not applicable to Windows
`LARGE_POOL_SIZE` | Uses maximum value limited by available memory
`LOG_BUFFER` | Starter database uses value set in Oracle Database kernel (no Windows-specific value). The Custom database creation option of Database Configuration Assistant enables you to customize the value for this parameter.
`SPIN_COUNT` | Uses default value set in Oracle Database kernel (no Windows-specific value)

## Displaying Initialization Parameter Values

Windows-specific parameter values can be viewed by using an ASCII editor to open the initialization parameter file:

    ORACLE_BASE\ORACLE_HOME\admin\db_name\pfile\init.ora

To display any parameter value (whether set in the initialization parameter file or the Oracle Database kernel), enter the following command at the SQL*Plus command prompt:

    SQL> SHOW PARAMETER parameter_name

where `parameter_name` is the name of a specific initialization parameter.

## Uneditable Database Initialization Parameters

Check the initialization parameters in Table 13-2 when creating a new database. They cannot be modified after you have created the database. See Chapter 3, "Postinstallation Database Creation on Windows" for details on creating a new database, including the part of the procedure where you modify these parameters.

Table 13-2 Uneditable Database Initialization Parameters

Parameter | Description
--- | ---
`CHARACTER SET` Foot 1 | Specifies database Globalization Support character set to use. This parameter can be set only when you create the database.
`DB_BLOCK_SIZE` | Specifies size in bytes of standard Oracle Database blocks.
`DB_NAME` | Specifies name of the database to be created. Database name is a string of eight characters or less. You cannot change the name of a database.

Footnote 1 Not an initialization parameter, but rather a clause in the `CREATE` `DATABASE` statement. See Chapter 3, "Postinstallation Database Creation on Windows" for an example of using this clause.

## Calculating Database Limits

Use size guidelines in this section to calculate Oracle Database limits.

Table 13-3 Block Size Guidelines

Type | Size
--- | ---
Maximum block size | 16,384 bytes or 16 kilobytes (KB)
Minimum block size | 2 kilobytes (KB)
Maximum blocks for each file | 4,194,304 blocks
Maximum possible file size with 16 K sized blocks | 64 Gigabytes (GB) (4,194,304 * 16,384) = 64 gigabytes (GB)

Table 13-4 Maximum Number of Files for Each Database

Block Size | Number of Files
--- | ---
2 KB | 20,000
4 KB | 40,000
8 KB | 65,536
16 KB | 65,536

Table 13-5 Maximum File Sizes

Type | Size
--- | ---
Maximum file size for a FAT file | 4 GB
Maximum file size in NTFS | 16 Exabytes (EB)
Maximum database size | 65,536 * 64 GB equals approximately 4 Petabytes (PB)
Maximum control file size | 20,000 blocks

Table 13-6 Shadow Process Memory

Release Number | Memory
--- | ---
Oracle9i release 2 (9.2) | 444 KB
Oracle9i release 1 (9.0.1) | 444 KB
Oracle8i release 8.1.7 | 335 KB
Oracle8i release 8.1.6 | 335 KB
Oracle8 release 8.1.3 | 265 KB
Oracle8 release 8.0.5 | 254 KB
Oracle8 release 8.0.4 | 254 KB