ASA Database Administration Guide
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      Database server options

-cw server option

Function 

Enables use of Address Windowing Extensions (AWE) on Windows 2000, Windows XP, and Windows Server 2003 for setting the size of the database server cache.

Syntax 

{ dbsrv9 | dbeng9 } -cw ...

Applies to 

Windows 2000, Windows XP, Windows Server 2003, and higher.

Description 

The amount of memory available for use as a database server cache is one of the key factors controlling performance. Because Windows 2000, Windows XP, and Windows Server 2003 support Address Windowing Extensions, you can use the -cw option to take advantage of large cache sizes based on the maximum amount of physical memory in the system.

*You must boot the operating system using the /3GB option to use a cache of this size.

When using an AWE cache, almost all of the available physical memory in the system can be allocated for the cache.

If you can set a cache of the desired size using a non-AWE cache, this is recommended because AWE caches allocate memory that can only be used by the database server. This means that while the database server is running, the operating system and other applications cannot use the memory allocated for the database server cache. AWE caches do not support dynamic cache sizing. Therefore, if an AWE cache is used and you specify the -ch or -cl options to set the upper and lower cache size, they are ignored.

For information about specifying the cache size, see -c server option.

To start a database server with an AWE cache, you must do the following

• Have at least 130 Mb of memory available on your system.

• If your system has between 2 Gb and 16 Gb of memory, add the /3GB option to the Windows boot line in the "[operating systems]" section of the boot.ini file.

  If your system has more than 16 Gb of memory, do not add the /3GB option to the Windows boot line in the "[operating systems]" section of the boot.ini file because Windows will not be able to address memory beyond 16 Gb.

• If your system has more than 4 Gb of memory, add the /PAE option to the Windows boot line in the "[operating systems]" section of the boot.ini file.

• Grant the "Lock pages in memory" privilege to the user ID under which the server is run. The following steps explain how to do this on Windows 2000.

  1. Log on to Windows as Administrator.

  2. From the Start menu, choose Settings > Control Panel.

  3. Open the Administrative Tools folder.

  4. Double-click Local Security Policy.

  5. Open Local Policies in the left pane.

  6. Double-click User Rights Assignment in the left pane.

  7. Double-click the Lock Pages In Memory policy in the right pane.

     The Local Security Policy Setting dialog appears.

  8. In the Local Security Policy Setting dialog, click Add.

     The Select Users or Groups dialog appears.

  9. Select the user ID from the list and click Add.

  10. In the Local Security Policy Setting dialog, click OK.

  11. Restart the computer for the setting to take effect.

If you specify the -cw option and the -c option on the command line, the database server attempts the initial cache allocation as follows:

1. The AWE cache is no larger than the cache size specified by the -c option. If the value specified by the -c option is less than 2 Mb, AWE is not used.

2. The AWE cache is no larger than all available physical memory less 128 Mb.

3. The AWE cache is no smaller than 2 Mb. If this minimum amount of physical memory is not available, AWE is not used.

When you specify the -cw option and do not specify the -c option, the database server attempts the initial cache allocation as follows:

1. The AWE cache uses 100% of all available memory except for 128 Mb that is left free for the operating system.

2. The AWE cache is no larger than the sum of the sizes of the main database files specified on the command line. Additional dbspaces apart from the main database files are not included in the calculation. If no files are specified, this value is zero.

3. The AWE cache is no smaller than 2 Mb. If this minimum amount of physical memory is not available, an AWE cache is not used.

When the server uses an AWE cache, the cache page size is at least 4 Kb and dynamic cache sizing is disabled. On 64-bit Windows platforms, the cache page size is at least 8 Kb.

For more information about dynamic cache sizing, see Using the cache to improve performance.

Example 

The following example starts a server named myserver that starts with a cache size of 12 Gb and loads the sample database:

dbeng9 -c 12G -cw asademo.db

See also 

-c server option