manikanta1207 (7/2/2013)
when do we take tail-log backup? and how can we take? wt cmds to be used
This sounds like a series of interview questions. My recommendation is that Gail's good answer has given you the end result but you need to readup about backups and TailLog backups in Books Online. Just in case you don't know what "Books Online" is, open SSMS then press the {f1} key and you're there (is the SQL Server "help" system).
--Jeff Moden
Change is inevitable... Change for the better is not.