HP 3000 Manuals HP 3000 Manuals
Restrictions
While the MAIL facility is supported on MPE XL, it is not as effective as
other types of IPC, for several reasons:
* Communication can take place only between processes in the same
process tree. Communication between processes in different trees is
not possible using MAIL.
* Each pair of processes requires a separate "mailbox" to transfer
messages between them. This is a less efficient use of system
storage than in other forms of IPC.
* Only upward and downward (parent/child) communication is possible.
Communication between sibling processes is not.
For these reasons, it is preferable to use other forms of IPC when
generating new applications on MPE XL. Use variables for simple IPC
within jobs and sessions; use the file system features to perform IPC
between different jobs and sessions in a network.