z/OS UNIX System Services environment effects on IP CICS sockets

The UNIX System Services provides controls on the number of sockets that can be opened concurrently by a single process (in a CICS® region). You can use this to limit the number of socket descriptors that a process can have, thereby limiting the amount of CICS and system resources a single process can use at one time.

Two specifications affect this limit:

The MAXFILEPROC parameter of the BPXPRMxx parmlib member, which specifies a default limit for any process in the system
FILEPROCMAX specification in the OMVS segment of the SAF profile for the CICS region's userid, which overrides the default; NOFILEPROCMAX can also be specified, which removes this limit

For more information about how MAXFILEPROC affects tuning applications, see z/OS UNIX System Services Planning. The z/OS® configuration tool, called Managed System Infrastructure (msys), contains additional information about the impacts of the UNIX MAXFILEPROC parameter settings.

For more information about the FILEPROCMAX specification, see the documentation provided for the SAF product in use on your system. If using RACF®, this can be found in the z/OS Security Server RACF Security Administrator's Guide

CICS/TS V2R3 and later does a set_dub_default causing each CICS Sockets task to run as its own OMVS process. Therefore, the MAXPROCSYS parameter must be large enough to accomodate the largest possible number of CICS Sockets tasks plus any other OMVS processes (CICS/TS itself always has at least 2 OMVS processes).