SQL Server Log: I/O is frozen on database DatabaseName

One more daily base SQL Server log message reported from one of our production server was

I/O is frozen on database model. No user action is required. However, if I/O is not resumed promptly, you could cancel the backup.

AND

I/O was resumed on database DATABASENAME. No user action is required.

First thing to note is that it’s just a message and not an error and no user action is required. On investigation for said production server, I found that our System Administrators has enabled SQL Server backup through VSS (Volume Shadow Copy Services) and this process actually freeze I/O temporarily to take shadow copy and release it back once process is complete. How it works read here.


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