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Always on\Database Mirroring Automatic Page Repair

A special thanks to Daniel Jones [daniel.jones.0543@gmail.com] for showing up interest and writing informative article for our blog (http://mssqlfun.com/).

 

Always on\Database Mirroring Automatic Page Repair

One of the most useful as well as hottest feature in SQL Server is mirroring of database. It is helpful for numerous of organizations that implements the successful as well as relatively high-availability of inexpensive strategies. However, in all the latest versions of SQL Server its service is being updated in numerous of ways such as database mirroring automatic page repair. It repairs the corrupt pages of the database. The automatic page repair is maintained by the database mirroring and Always on Availability Groups. After some specific types of errors, which had occurred in the database further make it in non-readable form. An availability replica tries to automatically repair the pages. The replica, which is unable to tread the page from another replica. If the request is implemented then, all the non-readable pages are replaced by the readable copies. It mainly resolves the occurrence of error.

Note: The automatic repair is completely differing from DBCC repair as all the database is stored by an automatic recovery of page.

Errors Occurred by Automatic Page-Repair

Database Mirroring of Automatic page repair efforts to repair in the data file through which an operation is failed as mentioned below:

  • Error 883

Description: Action is executed only if the OS implement CRC (cyclic redundancy check), which fails on the data.

Instances: ERROR_CRC. The operating system value for this error is 23

  • Error 824

Description: Logical

Instances: Logical data errors like checksum of torn write or bad page.

 

Techniques to Resolve Errors

  • Primary Database

The primary database of automatic page repair is tried when the state of database is SYNCHRONIZED. Moreover, the principal is still transferring log records for the database to the secondary. The elementary sequence of actions in an automatic attempt of page-repair are as mentioned:

  1. When an error of read comes up on a data page in the primary database then, the primary inserts row in the suspect_pages table with the correct status of an error. For database mirroring, the principal then, requests a copy of page from the mirror. For the Always On Availability Groups, the primary broadcasts the appeal to all the secondary’s and acquires the page from the first to react. The request identifies the ID and LSN, which is presently at end of flushed log. The page is marked as pending restore. This marks it inaccessible throughout the automatic page-repair effort. Attempts to utilize this page in the course of the repair attempt will fail with an error code 829.
  2. After getting page request, the secondary gaps till it has recreated the log up to the LSN stated in the request. After that, the mirror efforts to utilize the page in its database copy. If the page can be used, the mirror directs the copy of page to the principal. Otherwise, the secondary proceeds an error to the principal and the automatic page-repair effort fails.
  3. The primary methods the response, which holds the fresh copy of page.
  4. After the automatic page-repair effort fixes a suspect page, the page is noticeable in the suspect_pages table as reinstated.

 

  • Secondary Database

The input and output errors on pages, which happen on the secondary database are held in generally the similar way by mirroring and Always On Availability Groups.

  1. With mirroring of database, if the mirror comes upon one or more page errors of I/O when it rebuilds a log record, the session of mirroring arrives with the SUSPENDED state. Through Always On Availability Groups, if a replica of secondary meets one or more page errors of I/O when it recreates a log record, the secondary database enters the state of SUSPENDED. At that point, the mirror insets a row in the suspect_pages table with the suitable error status. The secondary then, requests a copy of page from the primary.
  2. The principal attempts to use the page in its database copy. If the page can be edited, the primary directs the copy of page to the secondary.
  3. If the mirror obtains copies of each page it has demanded, the secondary efforts to restart the mirroring session. If an automatic page-repair go fixes a suspect page, the page is clear in the suspect_pages table as reinstated.

If secondary does not obtain a page, which is requested from the principal, the automatic page-repair effort fails. With mirroring of database, the mirroring session leftovers suspended. With Always On Availability Groups, the secondary database leftovers suspended. If the mirroring session or secondary database is restarted manually, the corrupted pages will be again hit at the time of synchronization phase.

View Attempts of Automatic Page-Repair

The mentioned dynamic management previews return rows for the up-to-date automatic page-repair efforts on a given availability database, with maximum of 100 rows per database.

  • Always On Availability Groups:

sys.dm_hadr_auto_page_repair

Gives a row for each automatic page-repair effort on any database availability on availability replica, which is hosted for any group availability by server instance.

  • Database mirroring:

sys.dm_db_mirroring_auto_page_repair

Returns row for all automatic page-repair try on any database mirrored on the server instance.

Conclusion

It is important to repair the page to maintain the continuity of the work. Therefore, we have discussed Database mirroring automatic page repair in the above discussion that makes easy for users to remove the hurdle and understand it clearly.

Reference: Rohit Garg (http://mssqlfun.com/)

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How Row versioning impact tempDB ?

Scenario: DBA found that tempdDBdatabase usage is getting high and most of the size is consumed by row versioning. DBA raised the issue with application team running that query. Once Application team close the session, tempDB usage comes normal.

Question: Application tea raise concern “How can a select statement on table consume huge amount of resources in tempDB?”

Answer:

As per BOL (https://technet.microsoft.com/en-us/library/ms175492%28v=sql.105%29.aspx) : Row versioning-based isolation levels (RCSI – Read Committed Snapshot Isolation) reduce the number of locks acquired by transaction by eliminating the use of shared locks on read operations. This increases system performance by reducing the resources used to manage locks. Performance is also increased by reducing the number of times a transaction is blocked by locks acquired by other transactions. Row versioning-based isolation levels increase the resources needed by data modifications.

While updating the row in a table or index, the new row is marked with a value called the transaction sequence number (XSN), XSN is unique number and keeps updating with upcoming new command \ transactions. When updating a row, New version is generated. If DB is already having previous version of this row, previous version of the row is stored in the version store and the new version of the row contains a pointer to the old version of the row in the version store. New row version stores corresponding XSN value for reflecting the time the row was modified.

All version stores are linked in a chain. SQL Server keep running clean up task to remove old versions which are not in use. As long as a transaction is open, all versions of rows that have been modified by that transaction must be kept in the version store. This is the reason due to which long running open transaction can cause huge tempDB row versioning space.

Here, Row X is getting updated by multiple transactions (Tv,Tx,Ty,Tz) and each time new version store is created. When DB engine tries to clear old unused version stores, it found open transaction using version X. DB engine not able to clear any row version from version store after version X. Due to which TempDB size keeps increasing due to row versioning.

–Check Size of tempDB consumed by Version Store

SELECT SUM(VERSION_STORE_RESERVED_PAGE_COUNT) AS [VERSION STORE PAGES USED],

(SUM(VERSION_STORE_RESERVED_PAGE_COUNT)*1.0/128) AS [VERSION STORE SPACE IN MB],

SUM(INTERNAL_OBJECT_RESERVED_PAGE_COUNT) AS [INTERNAL OBJECT PAGES USED],

(SUM(INTERNAL_OBJECT_RESERVED_PAGE_COUNT)*1.0/128) AS [INTERNAL OBJECT SPACE IN MB],

SUM(USER_OBJECT_RESERVED_PAGE_COUNT) AS [USER OBJECT PAGES USED],

(SUM(USER_OBJECT_RESERVED_PAGE_COUNT)*1.0/128) AS [USER OBJECT SPACE IN MB],

SUM(UNALLOCATED_EXTENT_PAGE_COUNT) AS [FREE PAGES],

(SUM(UNALLOCATED_EXTENT_PAGE_COUNT)*1.0/128) AS [FREE SPACE IN MB]

FROM SYS.DM_DB_FILE_SPACE_USAGE;

–Find session using version store

SELECT A.*,B.KPID,B.BLOCKED,B.LASTWAITTYPE,B.WAITRESOURCE,B.DBID,B.CPU,B.PHYSICAL_IO,B.MEMUSAGE,B.LOGIN_TIME,B.LAST_BATCH,

B.OPEN_TRAN,B.STATUS,B.HOSTNAME,B.PROGRAM_NAME,B.CMD,B.LOGINAME,REQUEST_ID

FROM SYS.DM_TRAN_ACTIVE_SNAPSHOT_DATABASE_TRANSACTIONS A

INNER JOIN SYS.SYSPROCESSES B

ON A.SESSION_ID = B.SPID

Reference: Rohit Garg (http://mssqlfun.com/)

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Restrict user to login from single Host

Restricting user to login from single host may be sometimes required from security point and other business requirements. We can achieve it through SERVER LEVEL LOGON TRIGGER.

ALTER TRIGGER TR_CHECK_LOGIN_TEST_HOST
ON ALL SERVER
FOR LOGON
AS
BEGIN

DECLARE @HOSTNAME VARCHAR(48)
DECLARE @PROGNAME VARCHAR(100)

SELECT @HOSTNAME = HOST_NAME FROM SYS.DM_EXEC_SESSIONS
WHERE SESSION_ID = @@SPID

IF ORIGINAL_LOGIN() = ‘TEST’ AND @HOSTNAME =’HostName’
ROLLBACK;

END

Once you create above trigger, Login “TEST” will be able to connect from specified host only. Connection from any other host will be failed and face below error: –

You can also find related errors in SQL Server Error log as well.

Error: 17892, Severity: 20, State: 1.

Logon failed for login ‘TEST’ due to trigger execution. [CLIENT: <local machine>]

Error: 3609, Severity: 16, State: 2.

The transaction ended in the trigger. The batch has been aborted.

 

Reference: Rohit Garg (http://mssqlfun.com/)

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Write-Host || Cannot invoke this function because the current host does not implement it

Issue: While running powershell in SQL job step, I am getting below error: –

A job step received an error at line 13 in a PowerShell script. The corresponding line is ‘Write-Host “ServerName: ” $comp’. Correct the script and reschedule the job. The error information returned by PowerShell is: ‘Cannot invoke this function because the current host does not implement it.  ‘.  Process Exit Code -1.  The step failed.

 

Solution: SQL Server Agent allows users to directly run PowerShell scripts in SQL Server Agent. Internally this is implemented by reusing the SQLPS.EXE shell. When SQL Server Agent starts SQLPS.EXE, it does not do this through the console (there is no console attached).

 

When you run Write-Host, PowerShell asked to write on host console but due to no availability of HOST console, we got error.

I removed Write-Host to resolve issue.

 

Reference: Rohit Garg (http://mssqlfun.com/)

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Error While running PowerShell code from SQL Agent job – “Path Does Not Exist”

Issue: When I am running code from PowerShell console its running fine but when I execute it through SQL agent job step, I am getting below error: –

The job script encountered the following errors. These errors did not stop the script:  A job step received an error at line 14 in a PowerShell script. The corresponding line is ‘$files = Get-ChildItem “\\$comp\D$\*.xls”‘. Correct the script and reschedule the job. The error information returned by PowerShell is: ‘An object at the specified path \\ServerName\D$ does not exist.  ‘  A job step received an error at line 43 in a PowerShell script. The corresponding line is ‘    $str = Get-Content $i.FullName | Where-Object { ($_ -match ‘Alive’) }’. Correct the script and reschedule the job. The error information returned by PowerShell is: ‘Cannot bind argument to parameter ‘Path’ because it is null.  ‘.  Process Exit Code -1.  The step failed.

Solution: SQL Server Agent allows users to directly run PowerShell scripts in SQL Server Agent. Internally this is implemented by reusing the SQLPS.EXE shell. When SQL Server Agent starts SQLPS.EXE, It cannot access file system.

To access file system, you need to change the scope from SQL to filesystem.

You can do it by adding “cd C:” before executing filesystem commands.

 

Reference: Rohit Garg (http://mssqlfun.com/)

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Sequence – Long awaited feature

As per BOL (https://msdn.microsoft.com/en-us/library/ff878058(v=sql.110).aspx) : A sequence is a user-defined schema-bound object that generates a sequence of numeric values according to the specification with which the sequence was created. The sequence of numeric values is generated in an ascending or descending order at a defined interval and may cycle (repeat) as requested. Sequences, unlike identity columns, are not associated with tables. An application refers to a sequence object to receive its next value. The relationship between sequences and tables is controlled by the application. User applications can reference a sequence object and coordinate the values keys across multiple rows and tables.

This feature is really a good to have and this feature is same as Oracle’s sequence objects.  A sequence object generates sequence of unique numeric values as per specifications mentioned.

A sequence can be defined as any integer data type. If the data type is not specified, a sequence defaults to bigint. A sequence value is not effected by SQL server restart. Many people think sequence is similar to identity. But big difference is sequence object is independent of a table while identity columns are attached to a table.

Create Sequence

CREATE SEQUENCE TEMPSEQ AS INT

START WITH 1 — START WITH VALUE 1

INCREMENT BY 1– INCREMENT WITH VALUE 1

MINVALUE 0 — MINIMUM VALUE TO START IS 0

MAXVALUE 5 — MAXIMUM IT CAN GO TO 5

NO CYCLE — DO NOT GO ABOVE 5

CACHE 2 — INCREMENT 2 VALUES IN MEMORY RATHER THAN INCREMENTING FROM IO

Generate value from Sequence

SELECT NEXT VALUE FOR TEMPSEQ AS seq_no;

Error when Sequence reach to MAX value

Msg 11728, Level 16, State 1, Line 18

The sequence object ‘TEMPSEQ’ has reached its minimum or maximum value. Restart the sequence object to allow new values to be generated.

Alter Sequence to RESTART it from 1 or desired value

ALTER SEQUENCE TEMPSEQ RESTART WITH 1

 

Create Sequence with CYCLE mode, where value will be reset to MIN value when it reaches to MAX value

CREATE SEQUENCE TEMPSEQ_CYCLE AS INT

START WITH 1 — START WITH VALUE 1

INCREMENT BY 1– INCREMENT WITH VALUE 1

MINVALUE 0 — MINIMUM VALUE TO START IS 0

MAXVALUE 5 — MAXIMUM IT CAN GO TO 5

CYCLE — RESET to 0 once reached to MAX VALUE 5

CACHE 2 — INCREMENT 2 VALUES IN MEMORY RATHER THAN INCREMENTING FROM IO

Output of Sequence with CYCLE

SELECT NEXT VALUE FOR TEMPSEQ_CYCLE AS ID, NAME FROM SYS.OBJECTS

Sequence

Alter existing Sequence to set it to CYCLE mode

ALTER SEQUENCE TEMPSEQ CYCLE — RESET to 0 once reached to MAX VALUE 5

Use Sequence in Table as Default constraint.

Scenario: We need to generate token for each customer coming to meet him with HR & finance personal.

  1. Create Sequence

CREATE SEQUENCE TOKENNO AS INT

START WITH 1 — START WITH VALUE 1

INCREMENT BY 1– INCREMENT WITH VALUE 1

MINVALUE 0 — MINIMUM VALUE TO START IS 0

MAXVALUE 5000 — MAXIMUM IT CAN GO TO 5000

NO CYCLE — RESET to 0 once reached to MAX VALUE 5000

CACHE 200 — INCREMENT 200 VALUES IN MEMORY RATHER THAN INCREMENTING FROM IO

  1. Create Table with Sequence

CREATE TABLE HR_EXECUTIVE_MEETING

(TOKENNO INT DEFAULT (NEXT VALUE FOR TOKENNO), DESKNO INT)

 

CREATE TABLE FINANCE_EXECUTIVE_MEETING

(TOKENNO INT DEFAULT (NEXT VALUE FOR TOKENNO), DESKNO INT)

  1. Insert into table having Sequence

INSERT INTO HR_EXECUTIVE_MEETING(TOKENNO,DESKNO) VALUES(DEFAULT,22)

INSERT INTO FINANCE_EXECUTIVE_MEETING(TOKENNO,DESKNO) VALUES(DEFAULT,7)

  1. Check the table values

SELECT * FROM HR_EXECUTIVE_MEETING

SELECT * FROM FINANCE_EXECUTIVE_MEETING

Sequence

Reference: Rohit Garg (http://mssqlfun.com/)

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DMV-7 : Find Queries waiting for memory ?……..sys.dm_exec_query_memory_grants

sys.dm_exec_query_memory_grants DMV (Dynamic Management View), described by BOL as follows : http://msdn.microsoft.com/en-IN/library/ms365393.aspx

Returns information about the queries that have acquired a memory grant or that still require a memory grant to execute. Queries that do not have to wait on a memory grant will not appear in this view.

This DMV helps in finding queries that are waiting (or recently had to wait) for a memory grant. This particular DMV works with SQL Server 2005, 2008, and 2008 R2. There were some new columns added for SQL Server 2008 and above.

You should periodically run this query multiple times in regular intervals and need to look for rows returned each time. If you do see a lot of rows returned each time, then it could be an indication of internal memory pressure. It will help you to identify queries that are requesting relatively large memory grants, perhaps because they are poorly written or they’re missing indexes that make the query more expensive.

Query 1 : Details of queries required memory to execute

SELECT DB_NAME(ST.DBID) AS [DATABASENAME],

MG.REQUESTED_MEMORY_KB ,

MG.IDEAL_MEMORY_KB ,

MG.REQUEST_TIME ,

MG.GRANT_TIME ,

MG.QUERY_COST ,

MG.DOP ,

ST.[TEXT],

QP.QUERY_PLAN

FROM SYS.DM_EXEC_QUERY_MEMORY_GRANTS AS MG

CROSS APPLY SYS.DM_EXEC_SQL_TEXT(PLAN_HANDLE) AS ST

CROSS APPLY SYS.DM_EXEC_QUERY_PLAN(MG.PLAN_HANDLE) AS QP

ORDER BY MG.REQUESTED_MEMORY_KB DESC ;

Remarks

1. User required VIEW SERVER STATE permission on the server.

If you liked this post, do like on Facebook at http://www.facebook.com/mssqlfun

Reference : Rohit Garg (http://mssqlfun.com/)

DMV-6 : How well my store procedure doing ?……..sys.dm_exec_procedure_stats

sys.dm_exec_procedure_stats DMV (Dynamic Management View), described by BOL as follows : http://msdn.microsoft.com/en-us/library/cc280701.aspx

Returns aggregate performance statistics for cached stored procedures. The view con­tains one row per stored procedure, and the lifetime of the row is as long as the stored procedure remains cached. When a stored procedure is removed from the cache, the cor­responding row is eliminated from this view. At that time, a Performance Statistics SQL trace event is raised similar to sys.dm_exec_query_stats.

This DMV is new to SQL Server 2008 so you can use it only in SQL Server 2008 onwards. You can get similar data out of sys.dm_exec_cached_plans, which will work on SQL Server 2005. This DMV allows you to discover a lot of very interesting and important performance information about your cached stored procedures.

Query 1 : Details of cached procedures

SELECT CASE WHEN DATABASE_ID = 32767 THEN ‘RESOURCE’ ELSE DB_NAME(DATABASE_ID)END AS DBNAME

,OBJECT_SCHEMA_NAME(OBJECT_ID,DATABASE_ID) AS [SCHEMA_NAME]

,OBJECT_NAME(OBJECT_ID,DATABASE_ID)AS [OBJECT_NAME]

,*

FROM SYS.DM_EXEC_PROCEDURE_STATS

Query 2 : Details of procedure with total & average CPU, logical reads , logical writes & physical reads

SELECT CASE WHEN DATABASE_ID = 32767 THEN ‘RESOURCE’ ELSE DB_NAME(DATABASE_ID)END AS DBNAME

,OBJECT_SCHEMA_NAME(OBJECT_ID,DATABASE_ID) AS [SCHEMA_NAME]

,OBJECT_NAME(OBJECT_ID,DATABASE_ID)AS [OBJECT_NAME]

,CACHED_TIME

,LAST_EXECUTION_TIME

,EXECUTION_COUNT

,TOTAL_WORKER_TIME / EXECUTION_COUNT AS AVG_CPU

,TOTAL_ELAPSED_TIME / EXECUTION_COUNT AS AVG_ELAPSED

,TOTAL_LOGICAL_READS

,TOTAL_LOGICAL_READS / EXECUTION_COUNT AS AVG_LOGICAL_READS

,TOTAL_LOGICAL_WRITES

,TOTAL_LOGICAL_WRITES / EXECUTION_COUNT AS AVG_LOGICAL_WRITES

,TOTAL_PHYSICAL_READS

,TOTAL_PHYSICAL_READS / EXECUTION_COUNT AS AVG_PHYSICAL_READS

FROM SYS.DM_EXEC_PROCEDURE_STATS

ORDER BY AVG_LOGICAL_READS DESC

Remarks

1. User required VIEW SERVER STATE permission on the server.

2. This DMV will capture the details of 3 objects types :

a. SQL_STORED_PROCEDURE

b. CLR_STORED_PROCEDURE

c. EXTENDED_STORED_PROCEDURE

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Reference : Rohit Garg (http://mssqlfun.com/)

DMV-5 : Queries runing are adhoc or proc , single or multi use ?……..sys.dm_exec_cached_plans

sys.dm_exec_cached_plans DMV (Dynamic Management View), described by BOL as follows : http://msdn.microsoft.com/en-us/library/ms187404.aspx

Returns a row for each query plan that is cached by SQL Server for faster query execu­tion. You can use this dynamic management view to find cached query plans, cached query text, the amount of memory taken by cached plans, and the reuse count of the cached plans.

sys.dm_exec_cached_plans provide execution related details like no. of queries comes under adhoc or proc section. It help is understanding the query type & performance improvisation by looking into heavily running adhoc queries.

Query 1 : Memory used by cache plan of each database

SELECT

CP.CACHEOBJTYPE,

CP.OBJTYPE,

CASE WHEN ST.DBID = 32767 THEN ‘RESOURCEDB’ ELSE DB_NAME(ST.DBID) END AS DATABASE_NAME,

SUM(CASE WHEN CP.USECOUNTS <= 1 THEN 1 ELSE 0 END) AS SINGLE_USE_COUNT,

SUM(CASE WHEN CP.USECOUNTS > 1 THEN 1 ELSE 0 END) AS MULTI_USE_COUNT,

AVG(CASE WHEN CP.USECOUNTS > 1 THEN CP.USECOUNTS ELSE NULL END) AS MULTI_USE_AVG_USE_COUNT,

(SUM(CASE WHEN CP.USECOUNTS <= 1 THEN CP.SIZE_IN_BYTES ELSE 0 END) / (1024 * 1024)) AS SINGLE_USE_SIZE_IN_MBYTES,

(SUM(CASE WHEN CP.USECOUNTS > 1 THEN CP.SIZE_IN_BYTES ELSE 0 END) / (1024 * 1024)) AS MULTI_USE_SIZE_IN_MBYTES,

(SUM(CP.SIZE_IN_BYTES) / (1024 * 1024)) AS TOTAL_SIZE_IN_MBYTES

FROM

SYS.DM_EXEC_CACHED_PLANS AS CP

OUTER APPLY SYS.DM_EXEC_SQL_TEXT(CP.PLAN_HANDLE) AS ST

GROUP BY

CP.CACHEOBJTYPE,

CP.OBJTYPE,

CASE WHEN ST.DBID = 32767 THEN ‘RESOURCEDB’ ELSE DB_NAME(ST.DBID) END

ORDER BY

CP.CACHEOBJTYPE,

CP.OBJTYPE,

CASE WHEN ST.DBID = 32767 THEN ‘RESOURCEDB’ ELSE DB_NAME(ST.DBID) END

Query 2 : Find single-use, ad-hoc queries

SELECT ST.[TEXT] ,

CASE WHEN ST.DBID = 32767 THEN ‘RESOURCEDB’ ELSE DB_NAME(ST.DBID) END AS DATABASE_NAME,

CP.SIZE_IN_BYTES

FROM

SYS.DM_EXEC_CACHED_PLANS AS CP

CROSS APPLY SYS.DM_EXEC_SQL_TEXT(CP.PLAN_HANDLE) AS ST

WHERE CP.CACHEOBJTYPE = ‘COMPILED PLAN’

AND CP.OBJTYPE = ‘ADHOC’

AND CP.USECOUNTS = 1

ORDER BY CP.SIZE_IN_BYTES DESC

Remarks

1. User required VIEW SERVER STATE permission on the server.

If you liked this post, do like on Facebook at https://www.facebook.com/mssqlfun

Reference : Rohit Garg (http://mssqlfun.com/)

DMV-4 : Find top most expensive cached queries ?……..sys.dm_exec_query_stats

sys.dm_exec_query_stats DMV (Dynamic Management View), described in BOL as follows : http://msdn.microsoft.com/en-us/library/ms189741.aspx

Returns aggregate performance statistics for cached query plans. The view contains one row per query statement within the cached plan, and the lifetime of the rows are tied to the plan itself. When a plan is removed from the cache, the corresponding rows are eliminated from this view. An initial query of sys.dm_exec_query_stats might produce inaccurate results if there is a workload currently executing on the server. More accurate results may be determined by rerunning the query.

sys.dm_exec_query_stats provides a wealth of performance statistics for cached query plans. It’s a very useful DMV to get cached query details for performance & server load analysis.

Query 1 : Top 10 total CPU consuming queries

SELECT TOP 10

QT.TEXT AS STATEMENT_TEXT,

QP.QUERY_PLAN,

QS.TOTAL_WORKER_TIME AS CPU_TIME

FROM SYS.DM_EXEC_QUERY_STATS QS

CROSS APPLY SYS.DM_EXEC_SQL_TEXT (QS.SQL_HANDLE) AS QT

CROSS APPLY SYS.DM_EXEC_QUERY_PLAN (QS.PLAN_HANDLE) AS QP

ORDER BY TOTAL_WORKER_TIME DESC

Query 2 : Top 10 average CPU consuming queries

SELECT TOP 10

TOTAL_WORKER_TIME ,

EXECUTION_COUNT ,

TOTAL_WORKER_TIME / EXECUTION_COUNT AS [AVG CPU TIME] ,

QT.TEXT AS QUERYTEXT

FROM SYS.DM_EXEC_QUERY_STATS QS

CROSS APPLY SYS.DM_EXEC_SQL_TEXT(QS.PLAN_HANDLE) AS QT

ORDER BY QS.TOTAL_WORKER_TIME DESC ;

Query 3 : Top 10 I/O intensive queries

SELECT TOP 10

TOTAL_LOGICAL_READS,

TOTAL_LOGICAL_WRITES,

EXECUTION_COUNT,

TOTAL_LOGICAL_READS+TOTAL_LOGICAL_WRITES AS [IO_TOTAL],

QT.TEXT AS QUERY_TEXT,

DB_NAME(QT.DBID) AS DATABASE_NAME,

QT.OBJECTID AS OBJECT_ID

FROM SYS.DM_EXEC_QUERY_STATS QS

CROSS APPLY SYS.DM_EXEC_SQL_TEXT(SQL_HANDLE) QT

WHERE TOTAL_LOGICAL_READS+TOTAL_LOGICAL_WRITES > 0

ORDER BY [IO_TOTAL] DESC

Query 4 : Execution count of each query

SELECT QS.EXECUTION_COUNT,

QT.TEXT AS QUERY_TEXT,

QT.DBID,

DBNAME= DB_NAME (QT.DBID),

QT.OBJECTID,

QS.TOTAL_ROWS,

QS.LAST_ROWS,

QS.MIN_ROWS,

QS.MAX_ROWS

FROM SYS.DM_EXEC_QUERY_STATS AS QS

CROSS APPLY SYS.DM_EXEC_SQL_TEXT(QS.SQL_HANDLE) AS QT

ORDER BY QS.EXECUTION_COUNT DESC

Remarks

1. Statistics in the view are updated when a query is completed.

2. User required VIEW SERVER STATE permission on the server.

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Reference : Rohit Garg (http://mssqlfun.com/)

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