QUEUE_MANAGER section of the DFSDFxxx member

The QUEUE_MANAGER section of the DFSDFxxx member of the IMS PROCLIB data set specifies a limit on the 64-bit storage used for caching large messages and a threshold for the number of records to cache a Shared Queues retrieved message by the queue manager.

The section must begin with the header <SECTION=QUEUE_MANAGER>. The QUEUE_MANAGER section is optional and valid in DB/DC and DCCTL environments.

Syntax

Parameters

CACHE64_MAX_CACHE_SIZE=

Specifies the maximum size in GB of the queue manager 64-bit storage pool used for caching large messages, from 0 to 64. The default is 0 (no caching). The cache storage is in the private area of the IMS control region and is an IMS 64-bit storage manager pool named QMGRMESSAGECACHE. The QUERY POOL TYPE(STG64) command can be used to display the current attributes of this pool.

The CACHE64_MAX_CACHE_SIZE parameter is applicable only when IMS is running with shared message queues. It is ignored for non-shared queues systems, and on all systems with a version lower than IMS 15.3.

When the value of this parameter is 0, unspecified, or ignored, the queue manager does not allocate any 64-bit storage for caching, and does not cache large messages in 64-bit storage.

When the value of this parameter is 1 or greater, queue manager caching is enabled for certain types of messages. Message types that can be cached are:

APPC CM1 (synchronous) messages
OTMA CMA (synchronous) messages

When the number of records in a supported message type is 2 or greater, the second through last records of the message are cached in 64-bit storage when they are read from the shared queue (CQS) in the following situations:

When the total number of records in the message exceeds the value specified on the CACHE64_RECORD_THRESHOLD.
When the 31-bit queue pool of the queue manager has reached its upper limit, irrespective of the number of records in the message (if two or greater).
When the queue manager is unable to get a 31-bit buffer, irrespective of the number of records in the message (if two or greater). In this case, any records for the message that have been read into the 31-bit storage already (other than the first) are copied to 64-bit cache buffers, and the 31-bit buffers are released back to queue manager. Then the current and remaining records are put into 64-bit buffers.

CACHE64_RECORD_THRESHOLD=

Specifies the record number threshold to cache Shared Queues retrieved messages.

The Queue Manager always caches the second through last records of supported message types in the 64-bit storage if the total number of records in the message exceeds the number specified in CACHE64_RECORD_THRESHOLD= . The threshold can be from 0 to 2,147,483,647. The default is 10. This parameter only applies when IMS is running with shared message queues. It is ignored for non-shared queues systems, if the CACHE64_MAX_CACHE_SIZE parameter is zero, and on all systems with a version lower than IMS 15.3. If CACHE64_RECORD_THRESHOLD=0, no caching is done based on message record number; refer to the description of the CACHE64_MAX_CACHE_SIZE parameter.

Examples of the Queue Manager section

The following example sets the upper limit for the queue manager 64-bit cache pool to 1GB. The example also specifies that when the queue pool reaches its maximum limit or when there are no more 31-bit queue buffers available, the queue manager should cache the second through last records of eligible messages.

//*****************************************************************/
/* IMS Queue Manager Section                                            */
/******************************************************************/
<SECTION=UEUE_MANAGER>
CACHE64_MAX_CACHE_SIZE=1
CACHE64_RECORD_THRESHOLD=0
/******************************************************************/
/*                                                                */
/******************************************************************/

The following example sets the upper limit for the queue manager 64-bit cache pool to 2GB. The example also specifies that when the queue pool reaches its maximum limit or when there are no more 31-bit queue buffers available, the queue manager should cache the second through last records of eligible messages with number of records greater than 1.

//*****************************************************************/
/* IMS Queue Manager Section                                            */
/******************************************************************/
<SECTION=UEUE_MANAGER>
CACHE64_MAX_CACHE_SIZE=2
CACHE64_RECORD_THRESHOLD=1
/******************************************************************/
/*                                                                */
/******************************************************************/

//*****************************************************************/
/* IMS Queue Manager Section                                            */
/******************************************************************/
<SECTION=UEUE_MANAGER>
CACHE64_MAX_CACHE_SIZE=2
CACHE64_RECORD_THRESHOLD=99
/******************************************************************/
/*                                                                */
/******************************************************************/

The following example sets the cache option to none for the queue manager, which is the default option. As a result, no QMGRMESSAGECACHE pool will be allocated.

//*****************************************************************/
/* IMS Queue Manager Section                                            */
/******************************************************************/
<SECTION=UEUE_MANAGER>
CACHE64_MAX_CACHE_SIZE=0
/******************************************************************/
/*                                                                */
/******************************************************************/