Backup Log Database with truncate _only

It became deprecated Command and removed in 2008. You can achieve the same result by sending the file to the NUL blackhole

BACKUP LOG [DBNAME] TO DISK='NUL'
GO
DBCC SHRINKFILE("LOGFILE",0)


OR

alter database DBNAME set recovery simple
go
alter database DBNAME set recovery full
go
sp_helpdb 'DBNAME '
GO




use DBNAME
go
dbcc shrinkfile(LOGFILE,0)