The SHMEM privilege lets the user's process create global
sections and mailboxes (permanent and temporary) in memory shared
by multiple processors if the process also has appropriate PRMGBL, PRMMBX,
SYSGBL, and TMPMBX privileges. Just as in local memory, the space
required for a temporary mailbox in multiport memory counts against
the buffered I/O byte count limit (BYTLM) of the process.
The privilege also lets a user's process create or delete
an event flag cluster in shared memory using the Associate Common
Event Flag Cluster ($ASCEFC) or the Disassociate Common Event Flag
Cluster ($DACEFC) system service.