What happens when a disk gets full

When a queue manager is configured to use linear logging, the queue manager logging component reacts to a disk full condition in the following ways.

If the disk containing the log files becomes full, then:
  • The queue manager discovers this condition only when creating a new log file of the required size, which it does in advance of when it is needed.
  • It discovers the disk full condition when the operating system returns an error from the request to extend the file to the required size.
  • The queue manager issues message AMQ6708 to the queue manager error log.
  • A First Failure Support Technology (FFST) record is written into the system-wide errors directory. This record provides details of the disk full condition and should be retained should you need to contact IBM Support.

The log files are created at their fixed size, rather than being extended as log records are written to them. This means that IBM® MQ can run out of disk space only when it is creating a new file; it cannot run out of space when it is writing a record to the log. IBM MQ always knows how much space is available in the existing log files, and manages the space within the files accordingly.

From IBM MQ 9.1.0, when you use linear logging, you have the option to use:
  • Automatic management of log extents.

    See DISPLAY QMSTATUS for more information on the new log attributes.

    Also, see the following commands, or their PCF equivalents:
  • The options controlling the use of media images.
    See the ALTER QMGR command and ALTER QUEUES for more information on:
    • IMGINTVL
    • IMGLOGLN
    • IMGRCOVO
    • IMGRCOVQ
    • IMGSCHED

Circular logging returns a resource problem.

If you still run out of space, check that the configuration of the log in the queue manager configuration file is correct. You might be able to reduce the number of primary or secondary log files so that the log does not outgrow the available space.

You cannot alter the size of the log files for an existing queue manager. The queue manager requires that all log extents are the same size.