mssql vlf count 확인 및 축소

mssql db를 사용하다보면 vlf count가 증가하는 것을 볼수 있다.

vlf count가 증가하면 DML 및 로그 백업시 지연 이슈가 발생 할 수 있기 때문에 적절하게 축소해 주는것이 유리하다

2019 버전에서는 계속해서 증가하지 않도록 개선이 되었으나, 이하 버전에서는 관리가 필요

vlf 확인

SET NOCOUNT ON;
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;

-- 사용자 DB + TempDB 이름을 임시 테이블로 저장, 변수 선언
IF OBJECT_ID(N'tempdb..#DB') IS NOT NULL
BEGIN
	DROP TABLE #DB
END

CREATE TABLE #DB (name sysname, dbid smallint)

INSERT INTO #DB (name, dbid)
SELECT name, dbid FROM master.dbo.sysdatabases
--WHERE name not in ('master', 'msdb', 'model')
GO

print  '*** TR Log VLFs'
DECLARE @dbname SYSNAME
DECLARE @min_dbid SMALLINT
DECLARE @SQL VARCHAR(8000)
DECLARE @productversion VARCHAR(128)
DECLARE @Majorversion INT

SET @productversion = convert(VARCHAR(128), SERVERPROPERTY('ProductVersion'))
SET @Majorversion = convert(INT, left(@productversion, charindex('.', @productversion) - 1))

IF OBJECT_ID(N'tempdb..#LOGFILECNT') IS NOT NULL 
BEGIN
     DROP TABLE #LOGFILECNT
END


CREATE TABLE #LOGFILECNT (
	seq INT identity
	,dbname SYSNAME
	,logcount INT
	)

SET @min_dbid = 0

WHILE (@min_dbid IS NOT NULL)
BEGIN
	SELECT @min_dbid = MIN(dbid)
	FROM #DB
	WHERE dbid > @min_dbid

	IF (@min_dbid IS NULL)
		BREAK

	SELECT @dbname = NAME
	FROM #DB
	WHERE dbid = @min_dbid

	INSERT INTO #LOGFILECNT (dbname)
	SELECT @dbname

	SET @SQL = 'USE [' + @dbname + ']; '

	IF @Majorversion < 11
	BEGIN
		SET @SQL = @SQL + '
  CREATE TABLE #T1 (c1 nvarchar(30), c2 nvarchar(30), c3 nvarchar(30), c4 nvarchar(30), c5 nvarchar(30), c6 nvarchar(30), c7 nvarchar(30))
  INSERT INTO #T1 EXEC (''DBCC LOGINFO'')
  UPDATE #LOGFILECNT SET logcount = (SELECT count(*) FROM #T1)
  WHERE dbname = ''' + @dbname + '''
  DROP TABLE #T1
  '
	END
	ELSE
	BEGIN
		SET @SQL = @SQL + '
  CREATE TABLE #T1 (c1 nvarchar(30), c2 nvarchar(30), c3 nvarchar(30), c4 nvarchar(30), c5 nvarchar(30), c6 nvarchar(30), c7 nvarchar(30), c8 nvarchar(30))
  INSERT INTO #T1 EXEC (''DBCC LOGINFO'')
  UPDATE #LOGFILECNT SET logcount = (SELECT count(*) FROM #T1)
  WHERE dbname = ''' + @dbname + '''
  DROP TABLE #T1
  '
	END

	EXEC (@SQL)
END

SELECT dbname
	,logcount
FROM #LOGFILECNT
ORDER BY seq

IF OBJECT_ID(N'tempdb..#LOGFILECNT') IS NOT NULL 
BEGIN
     DROP TABLE #LOGFILECNT
END
GO

vlf 축소

-- checkpoit 발생
CHECKPOINT

-- 버퍼 클린
DBCC DROPCLEANBUFFERS

-- Log Backup
BACKUP LOG TestDB TO  DISK = N'e:\BACKUP\TestDB_log.trn' WITH NOFORMAT, NOINIT,  NAME = N'TestDB Backup', SKIP, NOREWIND, NOUNLOAD,  STATS = 10
GO

-- DB Shrink
USE TestDB
GO
DBCC SHRINKFILE (N'TestDB_log' , 0, TRUNCATEONLY)
GO



USE [master]
GO
ALTER DATABASE TestDB MODIFY FILE ( NAME = N'TestDB_log', SIZE = 10GB )
GO


dbcc loginfo(TestDB)