Exchange 2007 Continuous Replication and Circular Logging

I want to thank Neil for finding this. So in my lab I have a CCR cluster want just wanted to enable circular logging … I just couldnt get it work, looks like I missed a step :-o

http://technet.microsoft.com/en-us/library/bb331951.aspx

You can combine circular logging with continuous replication. In this configuration, you have a new type of circular logging called continuous replication circular logging (CRCL), which is different from the ESE circular logging described earlier in this topic. Whereas ESE circular logging is performed and managed by the Microsoft Exchange Information Store service, CRCL is performed and managed by the Microsoft Exchange Replication Service.

When enabled, ESE circular logging does not generate additional log files and instead overwrites the current log file when needed. However, in a continuous replication environment, log files are needed for log shipping and replay. As a result, when you enable CRCL, the current log file is not overwritten and closed log files are generated for the log shipping and replay process. Specifically, the Microsoft Exchange Replication Service manages CRCL so that log continuity is maintained, and logs are not deleted by the log deleter if they are still needed for replication. Therefore, enabling CRCL should not negatively affect replication.

In the release to manufacturing (RTM) version of Exchange 2007, combining circular logging with cluster continuous replication (CCR) or local continuous replication (LCR) is supported. However, we do not recommend this because it does not allow a roll-forward recovery after a backup has been restored. Exchange 2007 Service Pack 1 (SP1) also allows storage groups in a CCR, LCR or standby continuous replication (SCR) environment to have circular logging enabled. However, this practice is also not recommended for the reason indicated previously. When enabled in either of these environments, the functionality is CRCL and not ESE circular logging (also known as Joint Engine Technology (JET) circular logging). In a CCR, LCR, or SCR environment, you should always use the following process to enable or disable circular logging:

  1. Suspend continuous replication by using the Suspend-StorageGroupCopy cmdlet.
  2. Enable or disable circular logging. For detailed steps about how to enable or disable circular logging, see How to Enable or Disable Circular Logging for a Storage Group. (http://technet.microsoft.com/en-us/library/bb331968.aspx)
  3. Dismount and then mount the database in the storage group that is being enabled or disabled for circular logging.
  4. Resume continuous replication by using the Resume-StorageGroupCopy cmdlet.

For storage groups in an LCR environment, before running the Enable-StorageGroupCopy cmdlet to turn on LCR for a storage group, you must make sure that the current circular logging setting is detected and utilized by the Microsoft Exchange Information Store service by dismounting and then mounting the database in the storage group. While the Microsoft Exchange Information Store service requires that you dismount and then mount the database to detect and utilize the configuration change, the Microsoft Exchange Replication service is able to detect and utilize the configuration change dynamically and without any restart. Therefore, if the preceding procedure is not performed, a database can end up in a situation where the Microsoft Exchange Replication service considers circular logging to be off (or on) while the Microsoft Exchange Information Store service considers circular logging to be in the opposite state. This can result in log files being truncated prematurely.

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