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The SYS1.PARMLIB(BPXPRMxx) parameters

Use of certain CICS functions and running a large number of CICS systems in an LPAR mean that the default options, shipped in the BPXPRMxx members of SYS1.PARMLIB, are not sufficient. You must review the default options for the following functions:

Amending parameters in SYS1.PARMLIB(BPXPRMxx)

Both the use of XPLINK and of non-CICS APIs require some increase to the MAXPROCUSER and MAXPROCSYS values. If CICS is configured to use SSL, you might need to increase the MAXTHREADS and MAXTHREADTASKS values. These should exceed the MAXSSLTCBS SIT parameter.

If your system uses two or more of these facilities, corresponding further increases in the values for these parameters is appropriate.

The z/OS MAXPROCSYS parameter specifies the maximum number of processes that can be active at the same time, and allows you to manage system resources by limiting the number of processes that the system is to support. If you set the MAXPROCSYS value too low, regions might abend because CICS cannot create a process when attempting to attach a TCB. However, avoid setting the MAXPROCSYS value too high because this value is shared between all the address spaces in a z/OS system.

CICS uses at least two processes for each CICS region, which means that if you have a large number of CICS regions, you must set your system limit to handle these processes. The following table explains which TCBs become processes, depending on the CICS system:

Table 9. TCBs that become processes
TCB Is the TCB always a process? Description
Jobstep Yes The jobstep TCB is always created.
SO Yes The SO TCB is always created.
SL No The SL TCB is created unless the system initialization parameter, TCPIP=NO, is specified.
QR No The QR TCB becomes a process when an OTE TCB is attached (that is; L8, L9, J8, J9, X8, or X9).
SP No The SP TCB becomes a process, and the associated S8 TCBs are created and become threads only when SSL is used.
JVM (J8 and J9) No The number of J8 or J9 TCBs is controlled by the MAXJVMTCBS SIT parameter. J8 and J9 TCBs running active JVMs require one process each.

In summary, there is always a minimum of two processes for each CICS region, up to a minimum of seven processes for each region, depending on which additional TCBs you are running.

You can issue the following command to give you a list of the processes that are running on your system:

D OMVS, A=addressspaceid

addresspaceid is the address space that you want to query.

If you run this command at system startup, and again when your system has stabilized; for example, when peak J8 and J9 TCBs are running, you can calculate the most appropriate number for MAXPROCSYS.

For more information about changing BPXPRMxx parameters, monitoring system limits and calculating values for system resources, see z/OS Unix System Services Planning.

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