Message Advisor

Different product features can affect how you install BMC AMI Message Advisor for IMS . Various considerations and restrictions apply to installing and using Message Advisor .

Important

To serialize access to the RECON, Message Advisor now issues the MVS RESERVE macro, regardless of the value specified with the RESERVE_RECONS keyword.

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ConsiderationDiscussion
Memory usage
Message Advisor uses significant amounts of memory.

If restricted from using extensive EPVT, Message Advisor is forced to use time-consuming I/O processing (paging). To avoid paging, run Message Advisor in a multiple virtual storage (MVS) performance group with an unlimited working set size, or specify the INCORE=FIXED keyword. Otherwise, Message Advisor operation might be significantly slower.

When running head-to-head benchmarks with other message requeuer products, consider the effects of requeueing intersystem communication (ISC), multiple systems coupling (MSC), and conversational messages. In preliminary internal benchmark tests at BMC, Message Advisor appeared to run more slowly. This slowing occurs because Message Advisor requeues a significant number of ISC, MSC, and conversational messages that other products do not requeue. To avoid a slowdown, increase the number of IMS message queue buffers to safely accommodate the larger number of messages to be requeued and the increased rate at which Message Advisor accesses the IMS message queues.

The following additional factors can affect Message Advisor performance:

  • DELTA IMS VIRTUAL TERMINAL TSS buffers

    If you use DELTA IMS VIRTUAL TERMINAL and have Translate Subsystem Services (TSS) tables in your IMS system but do not use the Message Advisor Virtual LTERM Creation feature, you must specify an adequate number of TSS cache buffers. Otherwise, DELTA IMS VIRTUAL TERMINAL will spend more time reading the TSS tables during the requeue process. We recommend the following formula, where I is the number of DELTA IMS index blocks, T is the number of TSS table blocks, and B is the number of required TSS buffers:

    I + T = B

    For more information about displaying the number of index and table blocks, see Translate Subsystem Services Tables Open link .

  • IMS Message queue buffers

    If the IMS message queue buffers are set too low, IMS must perform more I/O to the queue data sets, which degrades performance. The larger the queue buffers on the target IMS system, the faster Message Advisor processes.

Requeueing messages across systems or IMS versions
Although Message Advisor does not specifically prohibit requeueing messages from one IMS system to another, or from one IMS version to another, be aware of the following constraints:
  • If you requeue from one IMS system to another, the systems must be identical; otherwise, unpredictable and possibly undesirable results might occur. For example, if one IMS system has a transaction defined that does not exist on the other IMS system, Message Advisor might, depending on command options, create a dynamic logical terminal (LTERM) of the same name and either requeue the messages there or discard them.

  • IMS prefixes usually vary from one level of IMS to another. Sometimes fields are in different locations, and new functions usually require adding new fields.

Message Advisor uses the IMS counter to tally the messages that are dequeued from a destination. Because the IMS counter 'wraps' at 64K, message number 65,536 becomes zero again. Even if more than 65,535 messages are queued to a destination, they will be dequeued; however, DEQUEUE will never report the deletion of more than 65,535. Because Message Advisor uses this same counter to calculate the totals on the DISPLAY Statistics Information panel, the total count will be inaccurate if a destination has more than 64K messages.

Some situations might require that Message Advisor not be initialized in the IMS control region, even if the product is licensed, installed, and customized. In these situations, add the JCL statement //MAQIGN DD DUMMY to the IMS control region that will not use Message Advisor . The presence of this DD statement will cause Message Advisor to skip all initialization and execution tasks for the duration of the control region and issue informational message BMC43373. To reactivate Message Advisor in the control region, remove the //MAQIGN DD statement and restart the control region.

Sort utilities
Message Advisor does not override any parameters that are set up by your sort utility. You must specify the SORT load library in the Message Advisor Server STEPLIB, or the SORT load modules must reside in LINKLIST.

The Message Advisor SORTCORE keyword on the CUSTOMIZE command set lets you reserve memory for your sort utility in the extended private area (EPVT) because Message Advisor will attempt to use all available EPVT memory.

If the SyncSort OS product’s CORE parameter is set to MAX, set the Message Advisor SORTCORE keyword to 4096 KB (the optimum size that we recommend). A larger value reduces the EPVT storage that is available for Message Advisor , which might affect performance. The default value of 4096 KB for SORTCORE is sufficient to process approximately 100,000 records in core.

Support for active XRF complexes
Message Advisor supports active Extended Recovery Facility (XRF) complexes.

You can install and operate Message Advisor  in an XRF complex. The following considerations apply to running Message Advisor in an XRF environment:

  • All XRF primary and alternate IMS systems must share a common checkpoint tracking data set.

    You must allocate the Message Advisor checkpoint tracking data set with SHAREOPTIONS (4,3).

    For details about allocating Message Advisor data sets, see Allocating Message Advisor data sets Open link .

  • IMS XRF systems that are running in the same LPAR and that have different IMSIDs must have separate Message Advisor IMSID options.

IMS XRF systems can share SPILL, EXTRACT, and UNLOAD data sets but are not required to do so. For more information about the data sets, see  Customizing BMC AMI Message Advisor for IMS Open link .

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