DCMT VARY Commands › DCMT VARY BUFFER › DCMT VARY BUFFER Parameters

DCMT VARY BUFFER Parameters

broadcast-parms

Indicates to execute the DCMT command on all or a list of data sharing group members.

Note: For more information about broadcasting and broadcast-parms syntax, see the section How to Broadcast System Tasks.

Buffer

Specifies the database buffer to be varied.

buffer-name

The name of the buffer.

PAges

Varies the number of pages currently in use by the specified buffer.

page-count

An integer in the range 3 to the maximum number of pages for the buffer, or 0, which closes the buffer. You can set the maximum number of pages for the buffer by using CREATE BUFFER, ALTER BUFFER, OR DCMT VARY BUFFER.

Use the DCMT DISPLAY BUFFER statement to determine the current page count for the buffer.

OPSYS storage

Acquires storage for the specified database buffer from the operating system. If your operating system supports extended addressing, CA IDMS attempts to get storage above the 16-megabyte line. If it cannot get storage above the line, it tries below the line. If enough storage is not available in the operating system, CA IDMS attempts to get storage from the DC/UCF storage pool.

DC storage

Acquires storage for the specified buffer from the DC/UCF storage pool. If an XA pool is defined that supports system storage, the storage is acquired above the 16 megabyte line.

Open

Makes the specified database buffer available to CA IDMS and allocates the initial number of pages specified for the buffer.

Close

Releases all storage for the specified database buffer.

Initial pages

Varies the initial number of pages specified for the buffer.

page-count

An integer in the range 3 through 16,777,214.

Additional pages

Specifies the number of pages acquired each time CA IDMS issues a storage request.

page-count

An integer in the range 1 through 16,777,214.

Maximum pages

Varies the largest number of pages that can be included in the database buffer.

page-count

An integer in the range 3 through 16,777,214.

PRefetch

Specifies whether prefetch processing is specified for the named buffer.

ON

Specifies that prefetch processing is enabled.

OFF

Specifies that prefetch processing is disabled.

nnn

Specifies the number of pages that must be in the buffer before prefetch is used for every read request.

If the prefetch limit is greater than the current number of pages in the buffer, the prefetch is used only if area sweeps are invoked or certain SQL access is performed.

More Information

• For more information about the fields in the output display of DCMT VARY BUFFER, see the section DCMT DISPLAY BUFFER.
• For more information about displaying buffer attributes, see the section DCMT DISPLAY BUFFER.
• For more information about creating buffers and changing their characteristics as defined in the database load module, see documentation of the CREATE BUFFER and ALTER BUFFER statements in the Database Administration Guide.
• For more information about minimizing contention among transactions for use of a buffer, see the Database Design Guide.
• For more information about guidelines for sizing a buffer and about prefetch processing, see the Database Administration Guide.