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Managing logs
Over time, some of the log records written become unnecessary for restarting the queue manager. If you are using circular logging, the queue manager reclaims freed space in the log files. This activity is transparent to the user and you do not usually see the amount of disk space used reduce because the space allocated is quickly reused.
Of the log records, only those written since the start of the last complete checkpoint, and those written by any active transactions, are needed to restart the queue manager. Thus, the log might fill if a checkpoint has not been taken for a long time, or if a long-running transaction wrote a log record a long time ago. The queue manager tries to take checkpoints often enough to avoid the first problem.
When a long-running transaction fills the log, attempts to write log records fail and some MQI calls return MQRC_RESOURCE_PROBLEM. (Space is reserved to commit or roll back all in-flight transactions, so MQCMIT or MQBACK should not fail.)
The queue manager rolls back transactions that consume too much log space. An application whose transaction is rolled back in this way cannot perform subsequent MQPUT or MQGET operations specifying syncpoint under the same transaction. An attempt to put or get a message under syncpoint in this state returns MQRC_BACKED_OUT. The application can then issue MQCMIT, which returns MQRC_BACKED_OUT, or MQBACK and start a new transaction. When the transaction consuming too much log space has been rolled back, its log space is released and the queue manager continues to operate normally.
If the log fills, message AMQ7463 is issued. In addition, if the log fills because a long-running transaction has prevented the space being released, message AMQ7465 is issued.
Finally, if records are being written to the log faster than the asynchronous housekeeping processes can handle them, message AMQ7466 is issued. If you see this message, increase the number of log files or reduce the amount of data being processed by the queue manager.
Parent topic:
Recovery and restart
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