Blitz Result: MSDB History Not Purged

SQL Server tracks the history of every backup.  It stores this data in the MSDB database.  That’s a system database, and by default, our system databases are stored on the C drive unless specified otherwise during installation.

This poses danger in a few different ways:

The C drive might fill up, causing MSDB writes to fail.  The system drive fills up more often than you might think – caused by careless users downloading huge files to their desktop (located on the system drive) or by Windows Updates downloading many files to a temporary folder on the system drive.

MSDB might grow to fill the C drive, causing Windows to fail.  In cases where we’re doing very frequent transaction log backups of a large number of databases, and we never purge MSDB, this database can grow to be big enough to threaten small C drives.  When the C drive fills, Windows fails hard.

The system drive is often slow.  In old versions of SQL Server, the system databases weren’t indexed well.  Combine this with slow local drives, and we’ve got a recipe for slow MSDB access.  In one case, during our nightly backup windows, 2/3 of the time was spent just updating MSDB!

Monitoring tools may query MSDB inefficiently.  We’ve seen cases where third party server monitoring tools constantly checked MSDB to make sure all databases were getting backed up, but their queries didn’t use indexes.  These queries can be the slowest thing on the server.

This part of our SQL Server sp_Blitz script checks to see if there’s MSDB backup history older than 60 days.  This by itself isn’t a problem – you may want to keep long periods of backup history in there just to do performance throughput reporting – but consider moving that data to Excel or your favorite reporting tool rather than hitting MSDB each time.

To Fix the Problem

Consider purging your MSDB backup history of data older than 60 days.  This is a part of SQL Server maintenance plans that can be just checked, but if your server has a large amount of history, this step will take a loooong time to run the first time.  As I noted in the MSDB bottleneck article, you may have to resort to extreme measures like changing system database foreign keys just to get the deletes to happen.

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