Avoiding short-on-storage conditions

To optimize your use of the CICS® dynamic storage areas and their storage cushions, and help to avoid short-on-storage conditions, follow these principles.

• The lower the number of concurrent transactions in the system, the lower the usage of virtual storage. If you can improve the internal response time for transactions, for example by minimizing physical I/O, you can decrease the usage of virtual storage.
• Avoid making large GETMAIN requests in your application programs.
  The storage cushion might not be large enough to satisfy a request for a large contiguous block of storage.
• Define programs as resident only where necessary.
  CICS cannot delete resident programs to reclaim space in a DSA, even if the programs are not in use.
• Use the CICS storage manager statistics to monitor storage cushion releases and storage request suspensions. If these incidents occur frequently, investigate the cause.
  If necessary, reduce the maximum number of user tasks (using the MXT system initialization parameter) to reduce the number of tasks that use main storage.
• Try to define a reasonable number of transactions as SPURGE(YES) and with a DTIMOUT value.
  Only transactions defined in this way can be purged during an SOS condition, if they have been waiting for storage for longer than the DTIMOUT value. If there are too few purgeable transactions, storage might become deadlocked in the CICS system.