In SQL Server Log Shipping process, we can see two files having extension name like .TUF and .WRK. These both files only generate on Log Shipping’s Secondary Server.
Actually SQL server manage internally handle the file copy process and restoration process at Secondary server using LS Copy and LS Restore job which are created at secondary server during log shipping initialization process. To manage the file copy process from Primary server to Secondary server, .WRK files temporarily generated. Means, The .wrk file got generate when the transaction log backups files are being copied from the backup location (Commonly at Primary Server end) to the secondary server by the agent job named as LS-Copy on the secondary, and when file copied completely at secondary server, they renamed to the .trn
extension. The temporary naming using the .wrk extension indicates/ensure that the files will not picked up by the restore job until successfully copied.
The .TUF file is the Transaction Undo File. It got generated only when we have configured the Log Shipping with Stand by Option only. As we know, in Stand by Log Shipping option, Secondary Database is available to user in read mode. In this scenario .TUF file Keeps Pending Transaction Which are in Log File came from Primary server, and when next Log Backup will come from primary server they can be synchronized at Secondary Server.
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