начиная с 2012 SQL Server такое прокатит:

USE MyDB
GO

DECLARE @MyDB_log nvarchar(max)
SET @MyDB_log=(SELECT name FROM sys.database_files where type_desc='LOG')

IF (select size*8 as SIZE_KB from sys.database_files 
where type_desc='LOG') > 5*1024*1024
BEGIN 
 ALTER DATABASE CURRENT SET RECOVERY SIMPLE 
 DBCC SHRINKFILE (@MyDB_log, 1024); 
 ALTER DATABASE CURRENT SET RECOVERY FULL

END
GO