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| Goodfellas |
 Posted: Sat Jan 08, 2011 8:54 pm Post subject: files |
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Acolyte
Joined: 26 Feb 2009
Posts: 70
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Hi,
Last edited by Goodfellas on Tue May 28, 2013 12:17 pm; edited 1 time in total |
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| skoobee |
| Posted: Sat Jan 08, 2011 10:16 pm Post subject: |
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Acolyte
Joined: 26 Nov 2010
Posts: 52
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The active log has a maximum size determined by the number of primary and secondary log files defined, and only needs to be big enough to hold msgs in transactions. Once a transaction has been completed, the active log no longer needs to hold it, and so space is freed.
Where the msgs can be found depends on the log type.
If linear, the msgs are stored either in the active log, or in the log extents which are not part of the active log. For example, in this case the log extents would initially be numbered from 1 to 500. As transactions use more space, new log extents would be created and the base of the active log would move away from extent 1, to the extent 500 prior to the newest number. The msgs would still be in the log, and are recoverable in the event of a failure. In this way, the log can contain any number of extents, for example, 1 - 10000. The earlier log extents are removed from even the inactive part of the log by running rcdmqimg, which saves the current state of queues and objects in the log, and moves log records from old to newer extents. Finally, the base of the log is reset to the earliest log extent which contains active data. Note that this is not the same as the active log.
If circular, the number of log extents remains the same. A checkpoint process is regularly carried out to reconcile the log records with the queue files. Once records have been reconciled, the log space can be reused. |
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