如何缩小SQL Server数据库日志文件

-----
SET NOCOUNT ON
DECLARE @LogicalFileName sysname,
        @MaxMinutes INT,
        @NewSize INT


USE     Marias            
 -- 要操作的数据库名
SELECT  @LogicalFileName = 'Marias_log'  
-- 日志文件名
@MaxMinutes = 10,               
-- Limit on time allowed to wrap log.
        @NewSize = 100                  
-- 你想设定的日志文件的大小(M)

-- Setup / initialize
DECLARE @OriginalSize int
SELECT @OriginalSize = size 
  FROM sysfiles
  WHERE name = @LogicalFileName
SELECT 'Original Size of ' + db_name() + ' LOG is ' + 
        CONVERT(VARCHAR(30),@OriginalSize) + ' 8K pages or ' + 
        CONVERT(VARCHAR(30),(@OriginalSize*8/1024)) + 'MB'
  FROM sysfiles
  WHERE name = @LogicalFileName
CREATE TABLE DummyTrans
  (DummyColumn char (8000) not null)


DECLARE @Counter   INT,
        @StartTime DATETIME,
        @TruncLog  VARCHAR(255)
SELECT  @StartTime = GETDATE(),
        @TruncLog = 'BACKUP LOG ' 
+ db_name() + ' WITH TRUNCATE_ONLY'

DBCC SHRINKFILE (@LogicalFileName, @NewSize)
EXEC (@TruncLog)
-- Wrap the log if necessary.
WHILE     @MaxMinutes > DATEDIFF 
(mi, @StartTime, GETDATE()) -- time has not expired
      AND @OriginalSize = (SELECT size 
FROM sysfiles WHERE name = @LogicalFileName)  
      AND (@OriginalSize * 8 /1024) > @NewSize  
  BEGIN -- Outer loop.
    SELECT @Counter = 0
    WHILE  ((@Counter < @OriginalSize / 16)
 AND (@Counter < 50000))
      BEGIN -- update
        INSERT DummyTrans VALUES ('Fill Log')  
        DELETE DummyTrans
        SELECT @Counter = @Counter + 1
      END   
    EXEC (@TruncLog)  
  END   
SELECT 'Final Size of ' + db_name() + ' LOG is ' +
        CONVERT(VARCHAR(30),size) + ' 8K pages or ' + 
        CONVERT(VARCHAR(30),(size*8/1024)) + 'MB'
  FROM sysfiles 
  WHERE name = @LogicalFileName
DROP TABLE DummyTrans
SET NOCOUNT OFF