The soft limit is the value of the current process limit that is enforced by the operating system. If a failure such as an abend occurs, the application might want to temporarily change the soft limit for a specific work item, or change the limits of child processes that it creates. For example, a larger server daemon might reduce the amount of virtual memory available to a spawned child. New processes receive the same limits as the parent process as long as the installation or the application do not alter those values and an identity change does not occur. The soft limits for CPUTIME, ASSIZE and MEMLIMIT can be affected by several MVS™ limits mechanisms.

MVS limits are the soft limits provided to z/OS® UNIX processes when z/OS UNIX services are invoked using TSO login, STC, or JCL. At the first request for a kernel service, the system dubs the program as a z/OS UNIX process. When a traditional MVS unit of work is first dubbed, the soft limits are normally obtained from MVS. The hard limit is normally obtained from BPXPRMxx if it is higher than the soft limit.

New processes that are created by a dubbed user receive the same soft and hard limits as the parent process if the installation has not changed the process limits and an identity change has not occurred.