I got bored (really bored) one weekend I decided to challenge myself. I had corruption within a specific table (localised within a page) with no backups handy only an old image of the data files. The challenge being salvage data without attaching the data files.
A quick video clip where I show two things.
Firstly I show how since SQL Server 2014 SP1+ the snapshot is no longer hidden then finally how I check that DBCC CHECKDB has ran successfully.
My database is in the recovery pending state and I want to get in and extract the data out into a new database, I have NO BACKUPS available so some data (even if it is dodgy) is better than nothing.
The title is adapted from a child-hood movie of mine and is my daily (database-related) WTF moment and it is my entry for this month’s T-SQL Tuesday found: http://www.pontop.dk/single-post/2017/03/07/Announcing-T-SQL-Tuesday-88-%E2%80%93-The-daily-database-related-WTF
Did you know that you can run DBCC CHECKDB (WITH PHYSICAL_ONLY) and issue page restores from SSMS (SQL Server Management Studio). I never, and I probably will never because I rather use TSQL – however I have only just seen this ( yes it’s been around for a while ) and felt like blogging about it.
I clicked on restore > page.
I corrupted page 126 and look it knows about it!
Yes it’s in bad shape – Level 24 severity.
SELECT * FROM [ZoraDB].[dbo].[people]
SQL Server detected a logical consistency-based I/O error: incorrect checksum (expected: 0xa154e798; actual: 0xa144e788). It occurred during a read of page (1:126) in database ID 11 at offset 0x000000000fc000 in file ‘C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\ZoraDB.mdf’. Additional messages in the SQL Server error log or system event log may provide more detail. This is a severe error condition that threatens database integrity and must be corrected immediately. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.
So SSMS is so good it will restore for you – and build the restore chain.
Hitting the SCRIPT button gives us:
USE [master] RESTORE DATABASE [ZoraDB] PAGE='1:126' FROM DISK = N'C:\SQLSERVER\ZoraDB.bak' WITH FILE = 1, NORECOVERY, NOUNLOAD, STATS = 5 -- Tail Log BACKUP LOG [ZoraDB] TO DISK = N'C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\Backup\ZoraDB_LogBackup_2016-12-15_09-51-17.bak' WITH NOFORMAT, NOINIT, NAME = N'ZoraDB_LogBackup_2016-12-15_09-51-17', NOSKIP, NOREWIND, NOUNLOAD, STATS = 5 RESTORE LOG [ZoraDB] FROM DISK = N'C:\SQLSERVER\ZoraLog.trn' WITH FILE = 1, NORECOVERY, NOUNLOAD, STATS = 5 RESTORE LOG [ZoraDB] FROM DISK = N'C:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\Backup\ZoraDB_LogBackup_2016-12-15_09-51-17.bak' WITH NOUNLOAD, STATS = 5 GO
SELECT * FROM [ZoraDB].[dbo].[people] (21 row(s) affected)
How cool is that?
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