How to clear logs on SQL SERVER

Ms SQL SERVER log growth is very fast, after a long time, log files will be very large, occupying a lot of hard disk space, so you need to regularly clear the log, you can use the following four methods:

Method 1:

1. Open the query analyzer and enter the command

Backup log database_name WITH NO_LOG

2. Choose "Enterprise Manager"> "right-click the database to be compressed"> "all tasks"> "shrink Database"> "contract file"> "select" Log File ">" contract to xxm "in the contract mode, here we will provide a minimum number of m that can be reduced. Enter this number directly and click OK.

Method 2:

Set checkpoints and automatically truncate logs

In general, the contraction of the SQL database does not greatly reduce the size of the database. Its main function is to shrink the log size. This operation should be performed regularly to avoid excessive database logs.

1. Set database mode to simple mode: Open the SQL Enterprise Manager, in the root directory of the console, open Microsoft SQL Server --> SQL Server group --> double-click to open your Server --> double-click to open the database directory --> select your database name (such as the user database) cwbase1) --> then right-click and select Properties --> Select Options --> select "simple" in the fault recovery mode, and then click OK to save

2. Right-click the current database to view the shrinking database in all tasks. Generally, the default settings in the database do not need to be adjusted. Click OK directly.

3. After shrinking the database, we recommend that you set your database attributes to the standard mode. The operation method is the same as the first one, because logs are often an important basis for restoring the database in case of exceptions.

Method 3: compress logs by SQL

Copy the code to the query analyzer, modify the three parameters (Database Name, log file name, and target log file size), and run

SET NOCOUNT ON

DECLARE @ LogicalFileName sysname,

@ MaxMinutes INT,

@ NewSize INT

USE tablename -- Name of the database to be operated

SELECT @ LogicalFileName = 'tablename _ log', -- log File Name

@ MaxMinutes = 10, -- Limit on time allowed to wrap log.

@ NewSize = 1 -- the size of the log file you want to set (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) + '8 K 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) + '8 K pages or '+

CONVERT (VARCHAR (30), (size * 8/1024) + 'mb'

FROM sysfiles

WHERE name = @ LogicalFileName

Drop table DummyTrans

SET NOCOUNT OFF

Method 4: delete a log file.

This method is risky because the log files of SQL server are not immediately written to the master database file. improper processing may cause data loss. 1. Disconnect all databases before the operation.

2. Database Separation

Database separation: Enterprise Manager-> server-> database-> cwbase1-> right-click-> database Separation

After separation, the cwbase1 database is deleted, but the data files and log files are retained.

3. delete a log physical file

Delete the physical LOG file and attach the database: Enterprise Manager> Server> database> right-click and choose attach database.

This method generates a new log with a size of more than 500 k.

Note: The first method is recommended. Before the operation, make sure that all operators have launched the system to disconnect the database.

Before performing the preceding operations, back up data!