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SQL,DBA,tuning,Trouble Shooting,Performance

Archive for July, 2014

DBCC help(‘?’) want to see all hidden DBCC command

Posted by Simon Cho on 07/22/2014

SQL 2005

DBCC HELP(‘?’)
DBCC TraceOn(2580)
DBCC HELP(‘?’)

SQL 2008 and above

DBCC HELP(‘?’)
DBCC TraceOn(2588)
DBCC HELP(‘?’)

 

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DBCC SHRINKFILE isn’t working even simple recovery mode.

Posted by Simon Cho on 07/15/2014

Log file Shrink has several dependency.

1. Log backup(or Checkpoint in simple recovery mode)

2. Replication

3. Mirroring

4. VLF

#1,2,3 can be check by this script

Declare @DBName varchar(255) = ‘test’
select log_reuse_wait_desc
from sys.databases where name= @DBName

So, most case, it’s ok.
But, only #4 can’t be checked by above script.

Please use this file to be able to check “StartOffset” for second VLF since LDF required minimum 2 VLFs.

DBCC LOGINFO

If it’s too big, need to refresh VLF.

big_Offset_VLF

 

 

 

 

But, unfortunately, refresh VLF isn’t simple.

http://www.sqlskills.com/blogs/kimberly/transaction-log-vlfs-too-many-or-too-few/
http://technet.microsoft.com/en-us/library/aa933049%28v=sql.80%29.aspx
http://www.brentozar.com/blitz/high-virtual-log-file-vlf-count/
http://sqlstudies.com/2013/08/26/the-effect-of-vlf-size-on-shrinking-the-log/

Ref. Log_reuse_wait (http://msdn.microsoft.com/en-us/library/ms178534.aspx)
0 = Nothing
1 = Checkpoint
2 = Log backup
3 = Active backup or restore
4 = Active transaction
5 = Database mirroring
6 = Replication
7 = Database snapshot creation
8 = Log Scan
9 = An AlwaysOn Availability Groups secondary replica is applying transaction log records of this database to a corresponding secondary database.
10 = For internal use only
11 = For internal use only
12 = For internal use only
13 = Oldest page
14 = Other (transient)

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SQL Agent Job server.(Centralized job server)

Posted by Simon Cho on 07/03/2014

http://www.informit.com/guides/content.aspx?g=sqlserver&seqNum=315

http://msdn.microsoft.com/en-us/library/ms180992(v=sql.120).aspx

 

Automated Administration Across an Enterprise

 

Automating administration across multiple instances of SQL Server is called multiserver administration. Use multiserver administration to do the following:

  • Manage two or more servers.
  • Schedule information flows between enterprise servers for data warehousing.

 

To take advantage of multiserver administration, you must have at least one master server and at least one target server. A master server distributes jobs to, and receives events from, target servers. A master server also stores the central copy of job definitions for jobs that are run on target servers. Target servers connect periodically to the master server to update their schedule of jobs. If a new job exists on the master server, the target server downloads the job. After the target server completes the job, it reconnects to the master server and reports the status of the job.

The following illustration shows the relationship between master and target servers:

Multiserver administration configuration

If you administer departmental servers across a large corporation, you can define the following:

  • One backup job with job steps.
  • Operators to notify in case of backup failure.
  • An execution schedule for the backup job.

 

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Drop certain query plan

Posted by Simon Cho on 07/02/2014

DECLARE @ObjName varchar(255)
SET @ObjName = ‘abc’
SELECT c.usecounts
, c.cacheobjtype
, c.objtype
, c.size_in_bytes
, t.text
, p.query_plan
, DB_NAME(p.dbid) AS DBNAME
, p.encrypted
FROM sys.dm_exec_cached_plans c
CROSS APPLY sys.dm_exec_sql_text(plan_handle) t
CROSS APPLY sys.dm_exec_query_plan (plan_handle) p
WHERE usecounts > 1 and t.text like ‘%’+@ObjName+’%’
AND t.text not like ‘%sys.dm_exec_cached_plans%’
GO

–DBCC FREEPROCCACHE (plan_handle);
–ex) DBCC FREEPROCCACHE (0x05000C00F01C44754021DDDA040000000000000000000000);
GO

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