Home » Posts tagged 'SQL'

Tag Archives: SQL

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/)

You can find and follow MSSQLFUN:-

http://www.facebook.com/mssqlfun

http://mssqlfun.com/feed

https://twitter.com/Rgarg86

Other Linked Profiles :-

http://www.sqlservercentral.com/blogs/mssqlfun/

http://social.msdn.microsoft.com/Profile/rohitgarg

http://www.toadworld.com/members/rohit-garg/blogs/default.aspx

http://beyondrelational.com/members/RohitGarg/default.asp

Error while loading Excel data into database

Issue: I am trying to load data from Excel 97 – 2003 sheet into a database table. I have written a simple SSIS package to do that, but unfortunately, it fails with error: –

 

Microsoft (R) SQL Server Execute Package Utility  Version 11.0.6020.0 for 64-bit  Copyright (C) Microsoft Corporation. All rights reserved.    Started:  2:02:37 AM  Error: 2016-12-19 02:02:37.91     Code: 0xC0209303     Source: ExcelImpot Connection manager “SourceConnectionExcel”     Description: The requested OLE DB provider Microsoft.ACE.OLEDB.12.0 is not registered. If the 64-bit driver is not installed, run the package in 32-bit mode. Error code: 0x00000000.  An OLE DB record is available.  Source: “Microsoft OLE DB Service Components”  Hresult: 0x80040154  Description: “Class not registered”.  End Error  Error: 2016-12-19 02:02:37.91     Code: 0xC001002B     Source: MAPTImpot Connection manager “SourceConnectionExcel”     Description: The ‘Microsoft.ACE.OLEDB.12.0’ provider is not registered on the local machine. For more information, see http://go.microsoft.com/fwlink/?LinkId=219816  End Error  Error: 2016-12-19 02:02:37.91     Code: 0xC020801C     Source: Data Flow Task 1 Source – Sheet1$ [38]     Description: SSIS Error Code DTS_E_CANNOTACQUIRECONNECTIONFROMCONNECTIONMANAGER.  The AcquireConnection method call to the connection manager “SourceConnectionExcel” failed with error code 0xC0209303.  There may be error messages posted before this with more information on why the AcquireConnection method call failed.  End Error  Error: 2016-12-19 02:02:37.91     Code: 0xC0047017     Source: Data Flow Task 1 SSIS.Pipeline     Description: Source – Sheet1$ failed validation and returned error code 0xC020801C.  End Error  Error: 2016-12-19 02:02:37.91     Code: 0xC004700C     Source: Data Flow Task 1 SSIS.Pipeline     Description: One or more component failed validation.  End Error  Error: 2016-12-19 02:02:37.91     Code: 0xC0024107     Source: Data Flow Task 1      Description: There were errors during task validation.  End Error  DTExec: The package execution returned DTSER_FAILURE (1).  Started:  2:02:37 AM  Finished: 2:02:37 AM  Elapsed:  0.733 seconds.  The package execution failed.  The step failed.

Cause: This error occurs when you try to execute 32-bit environment package in 64-bit system.

Solution 1: If you have project file of SSIS package or If you are running package other than SQL Agent jobs like calling from CMD.

Step 1: Navigate to Project-> [PROJECT_NAME] Properties.

Step 2: Navigate to “Debugging” option from left panel and from Right panel change Run64BitRuntime value to false.

Solution 2: If you need to execute package from SQL agent job only then you have readymade option available. Go to Job step and check below option.

 

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

You can find and follow MSSQLFUN:-

http://www.facebook.com/mssqlfun

http://mssqlfun.com/feed

https://twitter.com/Rgarg86

Other Linked Profiles :-

http://www.sqlservercentral.com/blogs/mssqlfun/

http://social.msdn.microsoft.com/Profile/rohitgarg

http://www.toadworld.com/members/rohit-garg/blogs/default.aspx

http://beyondrelational.com/members/RohitGarg/default.asp

Cumulative Update – 12 for SQL Server 2008 R2 Service Pack 1 Is Now Available !

The 12th cumulative update release for SQL Server 2008 R2 Service Pack 1 is now available for download at the Microsoft Support site. Cumulative Update 12 contains all the hotfixes released since the initial release of SQL Server 2008 R2 SP1.

 

 

Those who are facing severe issues with their environment, they can plan to test CU12 in test environment & then move to Production after satisfactory results.

For CU12 of SQL Server 2008 R2 SP1

· CU#12 KB Article: http://support.microsoft.com/kb/2828727

Previous Cumulative Update KB Articles:

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

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

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

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

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

%d bloggers like this: