Limitations:

     o  Maximum number (SHMMNI) of Shared Memory segments allowed in
        a system is 1024.

     o  Maximum size (SHMMAX) of a Shared Memory segment allowed is
        512 MB.

     o  Minimum size (SHMMIN) of a Shared Memory segment allowed is 1 byte.

    Prerequisites

     System V Shared Memory interfaces use file-backed global
     sections. These functions either create or delete the files based
     on request. The files are created in SYS$SPECIFIC:[DECC$SYSV_SHM].
     The System Manager or Administrator must create the directory
     using the following command before using the Shared Memory
     Functions:

         $ CREATE /DIRECTORY SYS$SPECIFIC:[DECC$SYSV_SHM] -
           /OWNER_UIC = [SYSTEM] -
           /PROTECTION = (S:RWE, O:RWE, G:RWE, W:RWE)

     If the SYS$SPECIFIC:[DECC$SYSV_SHM] directory does not exist, the
     directory SYS$SPECIFIC:[PSX$SEMAPHORES] will be used.