Does your z/OS queue manager have enough active log space? And how to fix it!
gwydiontudur |Apr 27 2017 Updated
I recently saw a queue manager at a customer site that was filling the active logs every 30 minutes at peak time, and only had 3 active logs defined. This means that they only had 90 minutes before their MQ workload would stop if they had a problem with archiving. Common causes of problems with archiving are running out of disk space or being unable to write to tapes.
Background
MQ writes data to the log whenever it processes persistent messages or transactions. It writes the data to active log data sets. When each active log data set fills up the data is offloaded to an archive log data set, which frees up the active log data set so that it can be used again. This process is called archiving. If all the active log data sets become full, for example because there is a problem with archiving, the queue manager won't be able to process any more persistent messages or transactions. So your important workload will grind to a halt. As a guideline, your z/OS queue manager should have enough active log space to run for 12-24 hours. This will give you time to fix any problems with archiving and avoid an outage caused by the active logs filling up.
What you need to do
So how do you go about adding more active log space if you need to do so?
Generally, we recommend making your active logs bigger, rather than just adding more data sets. This means that the queue manager will not need to take checkpoints when it switches active logs as often, which is good for performance. You may need to both make your active logs bigger and add more in order to have enough space.
Thanks to Colin Paice for providing the inspiration for this blog!