DAG log file truncation behaviour

Frequent Contributor

Is anyone able to point to anything from Microsoft that describes the log file truncation process? I'm looking to confirm that if we configure an Exchange node that contains only passive DB's and perform backups on this server, then the truncation of log files will be replicated to all members of the DAG that contain a copy of that DB, even though we are not backing up those servers specifically.

2 Replies

Hi. Dan Snape

If DAG is configured, it is recommended to back up all members when introducing an image backup solution.
Therefore, if you are a member whose backup is not proceeding, the transaction log file will not be replicated.

Best Response confirmed by Dan Snape (Frequent Contributor)

Yes it will. If you have an Exchange aware backup then backing up only a passive database is supported and works. Once the backup is complete and the current logs saved to backup the logs are truncated and this information is replicated across the DAG over RPC.


I had a client many years ago that blocked RPC across the inter-DAG network and truncation did not happen. Within seconds of fixing the network firewall TB of logs files got cleaned up on numerous servers across the world.