CODEWITHSUNDEEP
ibm-mq
debal
debal

Reputation: 1017

Primary and Secondary log files in MQ

Source

LogPrimaryFiles=3|2-254 (Windows)|2-510 (UNIX systems)

The log files allocated when the queue manager is created.

LogSecondaryFiles=2|1-253 (Windows)|1-509 (UNIX systems)

The log files allocated when the primary files are exhausted.

From what I understand, these log files are a part of transaction log.

Now, while creating the Queue Manager if I were to use the following settings,

LogPrimaryFiles=2  
LogSecondaryFiles=8 
LogFilePages=16384 
LogType=CIRCULAR 
LogBufferPages=0 
LogPath=/var/mqm/log/QMGRA/ 
LogWriteIntegrity=TripleWrite

I would like to know what happens after the 8 secondary log files are exhausted, i.e a scenario where all primary and secondary log files are filled.

Next, if I were to use these settings,

LogPrimaryFiles=2  
LogSecondaryFiles=8 
LogFilePages=16384 
LogType=LINEAR
LogBufferPages=0 
LogPath=/var/mqm/log/QMGRA/ 
LogWriteIntegrity=TripleWrite

In this case I would like to know what happens after,

  1. all primary log files are exhausted.
  2. all secondary log files are exhausted.

Also, when the Queue Manager needs to be restored, a restart of the Queue Manager is required. The queue manager will be restored from the last sync point that is defined in the transaction logs. However, I am confused as to where this sync point is located. Is it in the Primary log file or the secondary log file, or is it such that it may exist in either of them?

Upvotes: 4

Views: 5112

Answers (1)

T.Rob
T.Rob

Reputation: 31832

with either linear or circular logs, once the primary and secondary extents are filled with messages under syncpoint, the QMgr will start rolling back transactions to release some log space. There is a misconception that linear logs can handle any number of messages under syncpoint because they are not reused.

With linear logs, all persistent messages are captured in the log and those under syncpoint must fit within primary and secondary extents.

With circular logs, only messages under syncpoint are captured in the log.

The last point of consistency is always the oldest active log extent. Please see the Infocenter section Determining superfluous log files for more details. Alsop, have a look at Mission:Messaging: Circular logs vs. linear logs for a deeper explanation.

Upvotes: 4

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