Thanks master for your reply,

Before i shrink some data files as well as log file of other databases. After shrinking there no bad effect on other db. I am shrinking many times when found disk space issue. But today this spacific database's log file had about 900 MB available space, and i was not able to shrink that. So I thougt it might be used by some live transaction. If so, how can my collegue did that ? what he did differently ?

Is below command help me ?

USE DatabaseName

GO

DBCC SHRINKFILE(<TransactionLogName>, 1)

BACKUP LOG <DatabaseName> WITH TRUNCATE_ONLY

DBCC SHRINKFILE(<TransactionLogName>, 1)

GO

Is truncation on live environment will be advisable ?