Running without persistent sessions support

z/OS® Communications Server persistent sessions support is the default for a CICS® region, but you might choose to run a CICS region without this support if it is used only for development or testing. Specify NOPS for the PSTYPE system initialization parameter to start a CICS region without persistent sessions support. Running without persistent sessions support can enable you to increase the number of CICS regions in an LPAR.

If you have a large number of CICS regions in the same LPAR (around 500), with persistent sessions support available for all the regions, you might reach a z/OS limit on the maximum number of data spaces and be unable to add any more CICS regions. In this situation, when you attempt to start further CICS regions, you see messages IST967I and DFHSI1572, stating that the ALESERV ADD request has failed and the VTAM® (z/OS Communications Server) ACB cannot be opened. However, a region without persistent sessions support does not use a data space and so does not count towards the limit. To obtain a greater number of CICS regions in the LPAR:
  1. Identify existing regions that can run without persistent sessions support.
  2. Change the PSTYPE system initialization parameter for those regions to specify NOPS, and specify a zero value for the PSDINT system initialization parameter.
  3. Cold start the regions to implement the change.
You can then start further CICS regions with or without persistent sessions support as appropriate, provided that you do not exceed the limit for the number of regions that do have persistent sessions support.

If you specify NOPS (no persistent session support) for the PSTYPE system initialization parameter, a zero value is required for the PSDINT (persistent session delay interval) system initialization parameter.

When persistent sessions support is not in use, all sessions existing on a CICS system are lost if that CICS system, Communications Server, or z/OS fails. In any subsequent restart of CICS, the rebinding of sessions that existed before the failure depends on the AUTOCONNECT option for the terminal. If AUTOCONNECT is specified for a terminal, the user of that terminal waits until the GMTRAN transaction has run before being able to continue working. The user sees the Communications Server logon panel followed by the “good morning” message. If AUTOCONNECT is not specified for a terminal, the user of that terminal has no way of knowing (unless told by support staff) when CICS is operational again unless the user tries to log on. In either case, users are disconnected from CICS and need to reestablish a session, or sessions, to regain their working environment.