The TMPMBX privilege lets the user's process
create a temporary mailbox by executing the Create Mailbox and Assign
Channel ($CREMBX) system service.
Mailboxes are buffers in virtual memory that are
treated as if they were record-oriented I/O devices. A mailbox is
used for general interprocess communication. Unlike a permanent mailbox,
which must be explicitly deleted, a temporary mailbox is deleted automatically
when it is no longer referenced by any process.
Grant this privilege to all users of the system
to facilitate interprocess communication. System performance is not
likely to be degraded by permitting the creation of temporary mailboxes,
because their number is controlled by limits on the use of system
dynamic memory (BYTLM quota).