Specify the maximum amount of shared system storage pages that UNIX functions can use. This limit applies to the mmap, shmat, ptrace, and fork functions.
The fork service uses shared storage only when FORKCOPY(COW) is specified. Because the fork and ptrace functions use the shared storage pages as a boost to performance, the usage is not critical to the completion of these functions. For this reason, when the amount of shared storage pages being used reaches approximately 60% of the specified limit, these functions no longer use the shared storage to complete their function. Because the shmat() function is considered the most critical of the functions, it continues to use the shared storage pages until the total consumption reaches the specified limit. The mmap function continues to use the shared storage pages until total shared storage consumption reaches approximately 80% of the limit. Because each page of shared storage requires the associated consumption of extended system queue area (ESQA) storage, limiting the shared storage usage provides a way to limit the ESQA usage by UNIX users. If you use the __IPC_MEGA or __MAP_MEGA options, then the shared pages limits are not affected because MEGA does not affect the system ESQA overhead.
Default: 131072
Range: 0 to 32768000.