Plan the storage and performance requirements on z/OS

You must set realistic and achievable storage, and performance goals for your IBM MQ system. Use this topic help you understand the factors which affect storage, and performance.

This topic contains information about the storage and performance requirements for IBM MQ for z/OS®. It contains the following sections:

See, Where to find more information about storage and performance requirements for more information.


z/OS performance options for IBM MQ

With workload management, you define performance goals and assign a business importance to each goal. You define the goals for work in business terms, and the system decides how much resource, such as processor and storage, should be given to the work to meet its goal. Workload management controls the dispatching priority based on the goals you supply. Workload management raises or lowers the priority as needed to meet the specified goal. Thus, you need not fine-tune the exact priorities of every piece of work in the system and can focus instead on business objectives.

The three kinds of goals are:

    Response time
    How quickly you want the work to be processed

    Execution velocity
    How fast the work should be run when ready, without being delayed for processor, storage, I/O access, and queue delay

    Discretionary
    A category for low priority work for which there are no performance goals

Response time goals are appropriate for end-user applications. For example, CICS® users might set workload goals as response time goals. For IBM MQ address spaces, velocity goals are more appropriate. A small amount of the work done in the queue manager is counted toward this velocity goal but this work is critical for performance. Most of the work done by the queue manager counts toward the performance goal of the end-user application. Most of the work done by the channel initiator address space counts toward its own velocity goal. The receiving and sending of IBM MQ messages, which the channel initiator accomplishes, is typically important for the performance of business applications using them.


Determining z/OS workload management importance and velocity goals

For full information about workload management and defining goals through the service definition, see z/OS MVS Planning: Workload Management.

This section suggests how to set the z/OS workload management importance and velocity goals relative to other important work in your system.

Use the following service classes:

    The default SYSSTC service class

    • VTAM and TCP/IP address spaces
    • IRLM address space (IRLMPROC)
    Note: The VTAM, TCP/IP, and IRLM address spaces must have a higher dispatching priority than all the DBMS address spaces, their attached address spaces, and their subordinate address spaces. Do not allow workload management to reduce the priority of VTAM, TCP/IP, or IRLM to (or below) that of the other DBMS address spaces

    A high velocity goal and importance of 1 for a service class with a name that you define, such as PRODREGN, for the following:

    • IBM MQ queue manager and channel initiator address spaces
    • Db2 (all address spaces, except for the Db2-established stored procedures address space)
    • CICS (all region types)
    • IMS (all region types except BMPs)
    A high velocity goal is good for ensuring that startups and restarts are performed as quickly as possible for all these address spaces.

The velocity goals for CICS and IMS regions are only important during startup or restart. After transactions begin running, workload management ignores the CICS or IMS velocity goals and assigns priorities based on the response time goals of the transactions that are running in the regions. These transaction goals should reflect the relative priority of the business applications they implement. They might typically have an importance value of 2. Any batch applications using MQ should similarly have velocity goals and importance reflecting the relative priority of the business applications they implement. Typically the importance and velocity goals will be less than those for PRODREGN.


Library storage

You must allocate storage for the product libraries. The exact figures depend on your configuration, but an estimate of the space required by the distribution libraries is 80 MB. The target libraries require about 72 MB. Additionally, you require space for the SMP/E libraries.

The target libraries used by IBM MQ for z/OS use PDS or PDSE formats. Ensure that any PDSE target libraries are not shared outside a sysplex. For more information about the required libraries and their sizes and the required format, see the Program Directory for IBM MQ for z/OS, which can be downloaded from the from the IBM Publications Center (see IBM MQ Version 9.0 PDF documentation).


System LX usage

Each defined IBM MQ subsystem reserves one system linkage index (LX) at IPL time, and a number of non-system linkage indexes when the queue manager is started. The system linkage index is reused when the queue manager is stopped and restarted. Similarly, distributed queuing reserves one non-system linkage index. In the unlikely event of your z/OS system having inadequate system LXs defined, you might need to take these reserved system LXs into account.