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dc01bb · Posted: Sat Mar 14, 2009 8:31 am Post subject:

I've got a production queue manager whose active log files have grown too small. Several years ago, we had someone (who has since left) that resized the logs to suit the load that was present then. We've added workload, and it is time to expand again as the log files are switching every 8-10 minutes under peak load.

I've not seen a cohesive discussion of expansion of the log files in the IBM manuals, and it's not for a lack of looking... Neither is it discussed in the MP16 support pac performance and tuning guide (which, IMHO should be a part of the product documentation).

I did find a brief discussion here regarding log file expansion, which I tried successfully in a sandbox queue manager. That essentially said to

- quiesce the queue manager
- take appropriate backups
- allocate new, larger log files
- repro the data from the old log files into the new ones
- rename the new log files in place of the old ones
- alter zparms to increase the size of the archive offload files to suit the active log files

This worked just fine in my test queue manager.

I gave thought to whether I could re-allocate the log files while the queue manager was active, beginning with the least recently used log file, but note that they're all allocated while the queue manager is running.

I pondered the thought last evening whether it might be simpler to

- quiesce the queue manager
- take the necessary backups
- re-allocate all BSDS and LOG files new
- alter zparms accordingly
- restart the queue manager

If we presume that MQ has been quiesced in an orderly fashion, what would be the risks associated with expanding the log files in this manner. The only thing that I could think of would be that if we had to do a page set recovery and roll forward, we'd have to manage the logs being input to the process manually as the BSDS would have no recollection of past log datasets. Are there other impacts of basically starting with a brand new set of logs and allowing the catalog of logs maintained in the BSDS to start anew?
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IBM Certified Specialist - MQSeries