Estimating storage requirements for CMCI

To avoid possible storage problems when you use the CICS® management client interface (CMCI), you must specify appropriate levels of required storage in the CICS region. Any CMCI including the basic CMCI REST API requires 64-bit storage, and, if you have a CICSplex, auxiliary storage for the CMAS. If you are setting up the CMCI JVM server for the CMCI, you must also calculate the MVS storage required in 24-bit, 31-bit, and 64-bit storage.

Use the z/OS REGION parameter to set the limit for 24-bit and 31-bit (below-the-bar) storage. Use the z/OS® MEMLIMIT parameter to set the limit for 64-bit (above-the-bar) storage in your WUI region or CICS region, and the MAXAUXCPSM and MAXAUXTOTL CICSPlex® SM system parameters to set auxiliary storage for the CMAS.

About this task

If you are calculating storage requirements for a CICSPlex SM environment, consider the following factors:
  • Running the CMCI with large workloads can lead to short-on-storage situations on the WUI server and possible CMAS shutdowns caused by running out of auxiliary storage.
  • The CMCI stores retained results sets for the WUI server in 64-bit storage in the CICS region, in subpool WU_64 in the GCDSA.
  • During a CMCI request, the CMAS collects and stores the requested resource records, which are then backed up in auxiliary storage. Running requests concurrently through the CMCI multiplies the number of records held by the CMAS with each request.

If you are setting up the CMCI JVM server for the CMCI in your CICS region, the JVM server uses MVS storage in 24-bit, 31-bit, and 64-bit dressing areas in addition. Ensure that you include the storage requirement of the CMCI JVM server in your estimation.

Procedure

  1. Calculate the storage requirement for a typical request.
    Select the resource that is likely to generate the largest number of records in a request and multiply the number of records by the size of each record. See the appropriate table in CICSPlex SM resource tables to determine the record size.
  2. Calculate your total requirements for 64-bit storage for retained result sets.
    Estimate your expected maximum number of retained result records for a single request and multiply this figure by your estimate of the storage required for each request. For example, if you can have 100,000 CICS terminals in a single request, multiply this figure by the size of the resource record as determined in Step 1.
  3. If you are setting up the CMCI in a CICSPlex SM environment, estimate your auxiliary storage requirements for your CMAS.
    Estimate the maximum number of concurrent requests that you can expect and multiply this figure by your estimate of the storage required for each request as calculated in Step 2. You can derive your estimate of concurrent requests from the total number of users that you expect to be using the CMCI at any one time and how many simultaneous requests they are likely to make.
  4. Consider adding more storage for metadata.
    The CMCI stores all requested resource records for each request for a new retained result. For the initial request of a new resource type, for example, a first request for CICS programs, a small amount of attribute metadata is also stored. For large requests, the size of the attribute metadata and any other storage used while making the request is negligible compared to the storage required for records themselves. Consider adding an extra 2% to your final estimate to cover any extra metadata used internally by the CMCI on the WUI server. This extra metadata is not necessary for the CMAS calculation.

If you are setting up the CMCI JVM server, calculate its storage requirements also:

  1. The CMCI JVM server is a Liberty JVM server running in a WUI region of a CICSplex or a single CICS region. The JVM server requires MVS storage in 24-bit, 31-bit, and 64-bit addressing areas, in addition to the storage calculated in the previous steps.
    To calculate storage requirements for JVM servers, see Calculating storage requirements for JVM servers.

    The recommended maximum heap size for the CMCI JVM server is at least 2 GB in a CICSPlex SM environment, or 1 GB in a single CICS region (SMSS). Use it as an initial estimate and increase it as the scale of your environment needs.

What to do next

  • If the CMCI is installed in a CICSplex SM environment, use your estimate of auxiliary storage to set values for the MAXAUXCPSM and MAXAUXTOTL parameters on the CMAS associated with your WUI server.
  • Use your estimate of the 64-bit storage required for retained result sets plus the maximum heap size to help determine the z/OS MEMLIMIT value for your WUI region, or your single CICS region if you are running the CICS System Management Single Server for the CMCI. You must allow for the other CICS facilities that use 64-bit storage.

    For information about the MEMLIMIT value for CICS, and instructions to check the value of MEMLIMIT that currently applies to the CICS region, see Estimating, checking, and setting MEMLIMIT. For further information about MEMLIMIT in z/OS, see Limiting the use of private memory objects in the z/OS MVS Programming: Extended Addressability Guide.

  • Use your estimate of the 24-bit and 31-bit storage to help determine the z/OS REGION parameter for your region.