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Clear WebSphere MQ shared memory resources

 

When a WebSphere MQ queue manager is ended normally, the queue manager removes the majority of the IPC resources that it was using. A small number of IPC resources remain and this is as designed: some of the IPC resources are intended to persist between queue manager restarts. The number of IPC resources remaining varies to some extent, depending on the operating conditions.

There are some situations when a larger proportion of the IPC resources in use by a queue manager might persist after that queue manager has ended:

• If applications are connected to the queue manager when it stops (perhaps because the queue manager was shut down using endmqm -i or endmqm -p), the IPC resources used by these applications might not be released.

• If the queue manager ends abnormally (for example, if an operator issues the system kill command), some IPC resources might be left allocated after all queue manager processes have terminated.

In these cases, the IPC resources are not released back to the system until you restart (strmqm) or delete (dltmqm) the queue manager.

IPC resources allocated by WebSphere MQ are maintained automatically by the allocating queue managers. You are strongly recommended not to perform manual actions on or remove these IPC resources.

However, if it is necessary to remove IPC resources owned by mqm, follow these instructions. WebSphere MQ provides a utility to release the residual IPC resources allocated by a queue manager. This utility clears the internal queue manager state at the same time as it removes the corresponding IPC resource. Thus, this utility ensures that the queue manager state and IPC resource allocation are kept in step. To free residual IPC resources, follow these steps:

1. End the queue manager and all connecting applications.

2. Log on as user mqm.

3. Type the following:

   On Solaris, HP-UX, and Linux:

   /opt/mqm/bin/amqiclen -x -m QMGR 

   On AIX:

   /usr/mqm/bin/amqiclen -x -m QMGR

   This command does not report any status. However, if some WebSphere MQ-allocated resources could not be freed, the return code is nonzero.

4. Explicitly remove any remaining IPC resources that were created by user mqm.

If a non-mqm application attempted to connect to WebSphere MQ before starting any queue managers, there might still be some WebSphere MQ IPC resources remaining even after following the above steps. These remaining resources were not created by user mqm and there is no straightforward way to reliably recognize them. However, these resources are very small and are reused when WebSphere MQ is next restarted.

 

Parent topic:

WebSphere MQ and UNIX System V IPC resources

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