Setting process limits in z/OS UNIX

System-wide limits are defined in the BPXPRMxx parmlib member. Table 1 lists the BPXPRMxx statements that you can use to set system-wide limits. If you specify the SHRLIBMAXPAGES parameter, it will be accepted but will not have any impact on the system. The value that you specify will never be reached, because user-shared library objects are no longer supported.

Table 1. System-wide limits that can be defined in BPXPRMxx. This table lists the system-wide limits that can be defined in the BPXPRMxx parmlib member.
System-wide limits
IPCMSGNIDS	IPCSHMMPAGES	MAXPTYS
IPCMSGQBYTES	IPCSHMNSEGS	MAXRTYS
IPCMSGQMNUM	IPCSHMSPAGES	MAXSHAREPAGES
IPCSEMNIDS	IPCSHMNIDS	MAXUIDS
IPCSEMNSEMS	MAXASSIZE	SHRLIBMAXPAGES
IPCSEMNOPS	MAXMMAPAREA	SHRLIBRGNSIZE

Process-level limits are defined in the BPXPRMxx parmlib member. Table 2 lists the BPXPRMxx statements that you can use to set process-level limits.

Table 2. Process-level limits that can be defined in BPXPRMxx
Process-level limits
MAXASSIZE	MAXFILEPROC	MAXPROCSYS
MAXCORESIZE	MAXPIPEUSER	MAXQUEUEDSIGS
MAXCPUTIME	MAXPROCUSER	MAXTHREADS

MAXCPUTIME specifies the RLIMIT_CPU hard limit resource values that processes receive when they are dubbed a process. RLIMIT_CPU indicates the CPU time that a process is allowed to use, in seconds. The soft limit is obtained from MVS™. If the soft limit value from MVS is greater than the MAXCPUTIME value, the hard limit is set to the soft limit. This value is also used when processes are initiated by a daemon process using an exec after setuid(). In this case, both the RLIMIT_CPU hard and soft limit values are set to the MAXCPUTIME value.

For processes running in or forked from TSO or BATCH, the MAXCPUTIME value has no effect. A superuser can override this value by specifying a new time limit in the spawn inheritance structure on __spawn().
For processes running in or forked from TSO or BATCH, the MAXCPUTIME value has no effect. The TIME limit is inherited from the parent. If a TIME parameter is specified on the JCL for the started task, then that value is used. If not, then the TIME value is taken from the JES default TIME value.
For processes created by rlogind or another daemon, MAXCPUTIME is the time limit for the address space.

Table 3 lists the hard limits that can be defined in the RACF user profile.

Table 3. Hard limits that can be defined in the RACF user profile. This table lists the hard limits that can be defined in the RACF user profile.
Hard limit	Description
ASSIZEMAX	The maximum address space size (RLIMIT_AS) for the z/OS® UNIX user.
CPUTIMEMAX	The maximum CPU time (RLIMIT_CPU) for the z/OS UNIX user.
FILEPROCMAX	The maximum number of files per process for the z/OS UNIX user.
MEMLIMIT	The maximum storage above the bar (nonshared memory size). MEMLIMIT is initially set in the SMFPRMxx parmlib member.
MMAPAREAMAX	The maximum memory map size for the z/OS UNIX user.
PROCUSERMAX	The maximum number of processes per UID for thz/OS UNIX user.
SHMEMMAX	The maximum size of shared memory
THREADSMAX	The maximum number of threads per process for the z/OS UNIX user.