With backups of non-DAG configurations, truncation will occur after a successful backup.
With DAG replicated configurations, log truncation is delayed by the replication service until all the necessary log files have been replayed into all the other database copies.
After a backup you will see the following:
- Truncation requests can be seen with Event 2046 –Database log truncation has been requested for this database. Log truncation will occur on the active copy after the next log generation is created. Log truncation will occur automatically on the passive copies after that log file is copied.
- Event 225 - Information Store (xxx) Mailbox: No log files can be truncated
After these events look for the following:
- Event 9827 - Exchange VSS Writer has successfully completed the full or incremental backup of replicated database Mailbox'. The log files will be truncated after they have been replayed.
- Event 2157 - The replication instance for database Mailbox has copied and replayed multiple logs.
Now if you are running Exchange 2013 on Windows 2012, you can see more truncation events via the Exchange Crimson Channel event logs.
To view these logs
- Open Event Viewer;
- In the console tree, navigate to Applications and Services Logs -> Microsoft -> Exchange
- Under Exchange, select the crimson channel HighAvailability ->TruncationDebug
You should see three events that show that give some insight into the truncation process.
- Event 223 – Exchange servers report the replication service what logs files have been processed
- Event 224 – The replication service decides which files to truncate
- Event 299 – The replication service truncates the logs
These events will show you that the truncation process is working.