Reduce ldf file size

Question

I tried to reduce size of ldf file with the code

alter

@Dbname nvarchar(1000)

BEGIN

DECLARE

@qry nvarchar(4000)

SET

@qry='dbcc shrinkfile('+@Dbname+'_Log,TRUNCATEONLY) '

exec

(@qry)

END

but  i got error

"

Cannot perform a shrinkfile operation inside a user transaction. Terminate the transaction and reissue the statement."

how possible?

As

procedure reduceDatabaseSize