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| When does a QM free up disk space for an empty queue |
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| PeterPotkay |
 Posted: Wed Nov 26, 2008 10:58 am Post subject: When does a QM free up disk space for an empty queue |
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Poobah
Joined: 15 May 2001
Posts: 7722
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This question comes up every so often. Came across the below and figured I'd post it here, for the people that bother to use the search button:
http://www-01.ibm.com/support/docview.wss?rs=171&context=SSFKSJ&context=SSEP7X&dc=DB560&dc=DB520&uid=swg21173356&loc=en_US&cs=utf-8&lang=en
| Quote: |
Question
When does MQ reclaim storage allocated to a queue?
Cause
Your WebSphere MQ queue is loaded with messages and then the messages are removed, however the storage allocated to the queue is not released. The queue keeps its current size in regards to disk space.
Answer
Only after a queue is empty, and has not been opened by an application for several checkpoints, will the Q_Manager release the disk space.
This is working as designed. It is expensive to reserve disk space for a queue. As a result, and for performance reasons, MQ queue managers are slow to release disk space. |
_________________
Peter Potkay
Keep Calm and MQ On |
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| gbaddeley |
| Posted: Wed Nov 26, 2008 5:34 pm Post subject: |
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Jedi Knight
Joined: 25 Mar 2003
Posts: 2538
Location: Melbourne, Australia
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| Quote: |
| This question comes up every so often |
Yeah, such as http://www.mqseries.net/phpBB2/viewtopic.php?t=23858
Generally, MQ returns file space to as its internal scheduling permits. A couple of circumstances that help with this are:
When the last user closes an empty queue (CURDEPTH=IPPROCS=OPPROCS=0), all except the q file header is released.
When a checkpoint or media image is taken or the queue manager is stopped and restarted, empty space at the end of the file is released, or the file is compacted.
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Glenn |
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