Managing log files

Allocate sufficient space for your log files. For linear logging, you can delete old log files when they are no longer required.

Information specific to circular logging

If you are using circular logging, ensure that there is sufficient space to hold the log files when you configure your system (see Log defaults for IBM MQ and Queue manager logs ). The amount of disk space used by the log does not increase beyond the configured size, including space for secondary files to be created when required.

Information specific to linear logging

If you are using a linear log, the log files are added continually as data is logged, and the amount of disk space used increases with time. If the rate of data being logged is high, disk space is used rapidly by new log files.

Over time, the older log files for a linear log are no longer required to restart the queue manager or to perform media recovery of any damaged objects. The following are methods for determining which log files are still required:
Logger event messages
When a significant event occurs, for example a record media image, logger event messages are generated. The contents of logger event messages specify the log files that are still required for queue manager restart, and media recovery. For more information about logger event messages, see Logger events
Queue manager status
Running the MQSC command, DISPLAY QMSTATUS, or the PCF command, Inquire Queue Manager Status, returns queue manager information, including details of the required log files. For more information about MQSC commands, see Script (MQSC) Commands, and for information about PCF commands, see Automating administration tasks.
Queue manager messages
Periodically, the queue manager issues a pair of messages to indicate which of the log files are needed:
  • Message AMQ7467I gives the name of the oldest log file required to restart the queue manager. This log file and all newer log files must be available during queue manager restart.
  • Message AMQ7468I gives the name of the oldest log file needed for media recovery.

To determine "older" and "newer" log files, use the log file number rather than the modification times applied by the file system.

Information applicable to both types of logging

Only log files required for queue manager restart, active log files, are required to be online. Inactive log files can be copied to an archive medium such as tape for disaster recovery, and removed from the log directory. Inactive log files that are not required for media recovery can be considered as superfluous log files. You can delete superfluous log files if they are no longer of interest to your operation.

If any log file that is needed cannot be found, operator message AMQ6767E is issued. Make the log file, and all subsequent log files, available to the queue manager and try the operation again.

Note: When performing media recovery, all the required log files must be available in the log file directory at the same time. Make sure that you take regular media images of any objects you might want to recover to avoid running out of disk space to hold all the required log files.
For example, to take a media image of all your objects in your queue manager, run the rcdmqimg command as shown in the following examples:
On Windows 

rcdmqimg -m QMNAME -t all *
On UNIX and Linux® 

rcdmqimg -m QMNAME -t all "*"
Running rcdmqimg moves the media log sequence number (LSN) forwards. For further details on log sequence numbers, see Dumping the contents of the log using the dmpmqlog command. rcdmqimg does not run automatically, therefore must be run manually or from an automatic task you have created. For more information about this command, see rcdmqimg and dmpmqlog.
Note: Messages AMQ7467 and AMQ7468 can also be issued at the time of running the rcdmqimg command.