Message Queues

A process can create, read from, or write to a message queue. Each message is identified with a "type" number, a length value, and data (if the length is greater than zero).

Messages queues are good for handling small messages that are fed to a server. The intended design is that the message queue never get too deep.

A message can be read from a queue based on its type rather than on its order of arrival. Multiple processes can share the same queue. For example, a server process can handle messages from a number of client processes and associate a particular message type with a particular client process. Or the message type can be used to assign a priority in which a message should be dequeued and handled.

Deep queues and multiple message types for categorizing can affect performance.

Message queues are persistent for the duration of the current IPL. An application can write a message to a queue, and another job or address space can react to it right away or next week. Messages waiting in the queues are kept in kernel data spaces until they are received.

Use this panel to select system-wide message queue settings.

You can find more detailed help on the following elements of this window:

Number of unique queues on this system (IPCMSGNIDS)

Number of messages per queue (IPCMSGQMNUM)

Number of bytes per queue (IPCMSGQBYTES)

Bytes