On-premises Veeam backup for 365 uses Jet database (yes, the same as MS Exchange)
If you have 3 years retention for your data, it can quickly build up possibly filling your storage to the max. To fix this we can either add storage or if policy allows we can lower the retention and run a backup.
Then you will notice that the disk space is not automatically free’ed up. This is because Veeam for 365 uses Jet database(yes, the same as MS Exchange). So, the db files contain less data, but they are already grown bigger and won’t shrink automatically
So to resolve this, we can check the sizes, and compact the databases.
Before starting, confirm that no backup jobs or restore sessions are currently running.
Then stop both Veeam services on the proxy/server: ‘Veeam Backup for Microsoft 365 Service’ and ‘Veeam Backup Proxy for Microsoft 365 Service’.
Check free space in Jet databases Veeam for 365:
From an elevated command prompt run
esentutl /ms "<repo_path>\<year>\repository.adb"
You will see how much space can be compacted and free’ed.
Defrag:
For each year folder where whitespace is significant, run the defragmentation command. The /t parameter lets you place the temporary database on a different volume if you do not have enough free space on the same disk — the temp file will be as large as the database being defragged:
esentutl /d "<repo_path>\<year>\repository.adb" /t "<temp_path>\temp.adb"
— replace <repo_path>, <year>, and <temp_path> with your actual paths.
Work through each year folder (e.g., 2023, 2024, 2025) one at a time.
Important: esentutl will create a compacted copy of the database. Once it completes successfully for a given year folder, the original.adb file is replaced automatically. Do not interrupt the process mid-run, as this could leave the database in an inconsistent state.
Once defragmentation is complete for all relevant year folders, start the Veeam services again.
Hope that resolves your case 😊
