Exchange Server 2019 emails getting delayed due to high database log growth

Hi Klaus Cleo

Thank you for reaching out to Microsoft Q&A forum

Based on your description, I have conducted some research and it seems the cause comes from a failure in the log truncation process, which is supposed to delete committed transaction logs after a successful full or incremental backup, with circular logging disabled. This relies on proper integration between the backup solution, Volume Shadow Copy Service (VSS), and Microsoft Exchange Writer. If any component is misconfigured or malfunctioning, logs won’t be truncated. Common causes include misidentified backups (e.g., copy backup instead of full/incremental), VSS writer issues, database health problems (like unmounted databases or DAG replication failures), log commitment delays, or conflicts with services like the Exchange search indexer. When truncation fails, logs accumulate, consuming disk space and affecting performance.

As stated in:

Exchange Server storage configuration options | Microsoft Learn

Exchange Server data protection, Exchange disaster recovery, Exchange backup, Exchange VSS Writer

Therefore, in order to address this issue, you can adopt a structured troubleshooting approach starting with non-disruptive verification steps in Exchange Management Shell (EMS) or Command Prompt, progressing to targeted fixes, and including an emergency option if space is critically low. Kindly note thay you have to monitor the system after each step, as log truncation may sometimes take 2-3 days to fully occur, and I recommend reaching out to Microsoft Support if the problem persists. 

Verify the Last Backup:  Run this command to check if the last backup is recognized: 

Get-MailboxDatabase -Identity "DatabaseName" | Select Name, LastFullBackup, LastIncrementalBackup 

If the backup is outdated, make sure your backup tool is set for full/incremental backups (not a copy backup) and manually perform a full backup. 

Check VSS Writer Status:  Run this command to check the VSS writer status: 

vssadmin list writers | findstr /i "Exchange" 

If the VSS writer is in a failed state, restart the Microsoft Exchange Replication Service: 

Restart-Service MSExchangeRepl 

Review Event Logs:

In Event Viewer, go to Application logs and look for entries from MSExchangeIS and ESE. Check for missing truncation events (like Event ID 225) or other errors that might indicate a problem with backup integration.

Confirm Database Health: Run this to check the status of your database:

Get-MailboxDatabase -Identity "DatabaseName" | Select Name, Mounted, Status 

This summary is based on my findings from the community and several relevant threads. However, it may not accurately reflect the behavior in question. To help you reach your goal more effectively, I recommend posting a thread on the Microsoft Tech Community forum. It’s a great platform for deeper technical discussions and connecting with individuals who have hands-on experience and expertise. They’re best positioned to provide guidance and valuable insights on this topic.   

Hope my answer will help you, for any further concern, kindly let me know in the comment section

 Best regards

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