Problem

How to troubleshoot suspect database problem? How to bring it back online? What are the do you need to perform once the database is online?

Solution

Step 1: Bring the database online using below script

USE Master

GO

 

— Determine the original database status

SELECT [Name], DBID, Status

FROM master.dbo.sysdatabases

GO

 

— Enable system changes

sp_configure ‘allow updates’,1

GO

RECONFIGURE WITH OVERRIDE

GO

 

— Update the database status

UPDATE master.dbo.sysdatabases

SET Status = 24

WHERE [Name] = ‘SuspectedDatabaseName’

GO

 

— Disable system changes

sp_configure ‘allow updates’,0

GO

RECONFIGURE WITH OVERRIDE

GO

 

— Determine the final database status

SELECT [Name], DBID, Status

FROM master.dbo.sysdatabases

GO

Step 2: Check for database corruption. This is very important step please execute it.

• DBCC CHECKDB – Validate the overall database integrity
• DBCC CHECKCATALOG – Validate the system catalog integrity
• DBCC CHECKTABLE – Validate the integrity for a single table

Step 3: To resolve the corruption issue, please execute below commands

• Drop and Recreate Index(es)
• Move the recoverable data from an existing table to a new table
• Update statistics
• DBCC UPDATEUSAGE
• sp_recompile

Step 4: Repeat Step 2 to validate all the corruption occurred

The easiest solution to implement clustering in MySQL is DRBD and Heartbeat.

DRBD: The Distributed Replicated Block Device (DRBD) is a software-based, shared-nothing, replicated storage solution mirroring the content of block devices (hard disks, partitions, logical volumes etc.) between servers.

DRBD mirrors data

• In real time. Replication occurs continuously, while applications modify the data on the device.
• Transparently. The applications that store their data on the mirrored device are oblivious of the fact that the data is in fact stored on several computers.
• Synchronously or asynchronously. With synchronous mirroring, a writing application is notified of write completion only after the write has been carried out on both computer systems. Asynchronous mirroring means the writing application is notified of write completion when the write has completed locally, but before the write has propagated to the peer system

You can download DRDB from below site

http://www.drbd.org/download/packages/