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v If CICS determines that it cannot recover the session without unbinding and
rebinding it.
The result in each case is as if CICS has restarted following a failure without
VTAM persistent sessions support.
In some other situations APPC sessions are unbound. For example, if a bind was in
progress at the time of the failure, sessions are unbound.
With multinode persistent sessions support, if a VTAM or z/OS failure occurs and
the TPEND failure exit is driven, the autoinstalled terminals that are normally
deleted at this point are retained by CICS. If the session is not reestablished and
the terminal is not reused within the AIRDELAY interval, CICS deletes the TCTTE
when the AIRDELAY interval expires after the ACB is reopened successfully.
Situations in which VTAM does not retain sessions
When VTAM persistent sessions support is in use for a CICS region, in some
circumstances VTAM does not retain LU-LU sessions.
v If you close VTAM with any of the following CICS commands:
– SET VTAM FORCECLOSE
– SET VTAM IMMCLOSE
– SET VTAM CLOSED
v If you close the CICS node with the VTAM command VARY NET INACT ID=applid.
v If your CICS system performs a normal shutdown, with a PERFORM SHUTDOWN
command.
If single-node persistent sessions support (SNPS), which is the default, is specified
for a CICS region, sessions are not retained after a VTAM or z/OS failure. If
multinode persistent sessions support (MNPS) is specified, sessions are retained
after a VTAM or z/OS failure.
Running without persistent sessions support
VTAM 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 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.
40 CICS TS for z/OS 4.1: Recovery and Restart Guide
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