In MS SQL Server database, a page is used as the most primitive unit of storage as the space allocated to every database file. And a collection of eight pages is called an extent, which is used to manage the pages. However, sometimes SQL Server is unable to read through the properties of these pages. Such problems can invariably occur due to various issues such as virus infections, power outages, hardware problems, abrupt system shutdown when the database is open, etc. In such cases, you should find out the exact cause of corruption and try to isolate it. If any of the methods do not succeed, then you should use a third-party SQL repair software to repair SQL database.

Consider a scenario wherein you encounter the following error message while working on an MS SQL Server 2008 database:

"Process ID %d attempted to unlock a resource it does not own: %.*ls. Retry the transaction, because this error may be caused by a timing condition. If the problem persists, contact the database administrator."

Cause:

The root cause of this problem is that there are some structural problems within the database, which have resulted in database corruption. Due to the database corruption, SQL Server is trying to incorrectly trying to unlock a page, which is already unlocked.

Resolution:

To resolve this erroneous situation, you should perform the following methods:

Restore from backup: You should check if the database has an updated and clean backup. If yes, then you should use it to restore the database.

Use DBCC CHECKDB: If the backup is not updated, then you should run the DBCC CHECKDB utility first without any repair clause to know the extent of damage. Then, run it again with the suggested repair clause. Try to reconnect to the database. It should get connected now.

However, if the problem is persisting then you should use a third-party .MDF repair software to repair SQL database. Such MDF repair tools are read-only in nature that do not overwrite the existing database while scanning.

Stellar Phoenix SQL Data Recovery is an SQL repair software that repairs SQL database from all instances of logical corruption. It is specifically designed to repair MDF files created for MS SQL Server 7.0, 2000, 2005, and 2008. This MDF file repair utility repairs various database objetcs such as tables, NDF files, collations, stored procedures, triggers, defaults, etc. In addition, it is able to preserve the relationships among tables. This MS SQL Server repair tool is compatible with Windows 7, Vista, Server 2003, XP, and 2000.

Ref: http://www.americanchronicle.com/articles/view/170065