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Shared memory on AIX

 

The AIX model for System V shared memory differs from other UNIX platforms, in that a 32-bit process can only attach to 10 WebSphere MQ memory segments concurrently.

A typical 32-bit WebSphere MQ application requires two WebSphere MQ memory segments attached for every connected queue manager. Every additional connected queue manager requires one further WebSphere MQ memory segment attached.

During the MQCONN operation an additional shared memory segment is required. In a threaded process where multiple threads are connecting to the same queue manager, ensure an additional memory segment is available for every connected queue manager.

A 64-bit process is not limited to attaching to only 10 WebSphere MQ memory segments concurrently. A typical 64-bit WebSphere MQ application requires three WebSphere MQ memory segments for every connected queue manager. The connection of additional queue managers typically requires two further WebSphere MQ memory segments for every connected queue manager. Applications that connect to heavily loaded queue managers can require additional memory segments.

WebSphere MQ V5.3 recommended the use of the environment variable EXTSHM to allow 32-bit applications to connect to more than 10 WebSphere MQ memory segments at a time. With WebSphere MQ V6, the setting of the EXTSHM variable has no effect on the shared memory used by WebSphere MQ.

 

Parent topic:

WebSphere MQ and UNIX System V IPC resources

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