日志文件比较大时，使用语句减少大小。

USE DATABASENAME;

GO

-- Truncate the log by changing the database recovery model to SIMPLE.

ALTER DATABASE DATABASENAME

SET RECOVERY SIMPLE;

GO

-- Shrink the truncated log file to 1 MB.

DBCC SHRINKFILE (DATABASENAME_Log, 1);

GO

-- Reset the database recovery model.

ALTER DATABASE DATABASENAME

SET RECOVERY FULL;

GO