LSN Chain and VM Snapshot

There is an option in VM backup tool for performing Transaction Log clearing. In our case it was VEEAM backup tool. Other tools like Hyper V backup, V ranger  are other backup tools.

During VM snapshot, there is an option to clear the LOG as mentioned in the blog. By default the option to Truncate logs will be enabled.
The way that these tools clear the transaction log during a VM snapshot backup is by issuing a subsequent command to the SQL Server,

**BACKUP LOG <database_name> TO DISK =’NUL’, **

which dumps the transaction log records to nowhere, essentially throwing them away completely and thus breaking the log backup chain. In the sense, when you issue the above command, no backup files are getting generated and it simply truncates log, which in turn makes our day horrible. I have documented these details from top to bottom in my blog mentioned below.

http://sqldeepdives.blogspot.in/2014/04/lsn-chain-break-and-vm-backup.html