You may come across SQL Server database corruption if the registry checkpoint of SQL Server agent is missing. In this case, SQL Server Agent cannot be found and MS SQL Server cannot start up. In such situations, MDF (Master Database File) of SQL Server becomes inaccessible and you come across critical data loss situations. To work around this problem, MDF Database Recovery is essential, if you do not have an updated backup.

As a practical example of this problem, consider this scenario:

• The Registry checkpoint of SQL Server Agent is missing due to some unexpected deletion or unexpected corruption problems in the clustered instance of MS SQL Server 2008.

• Clustered instance of Microsoft SQL Server 2008 is repaired.

In the above scenario, you cannot find the registry subkey, which is associated with the SQL Server Agent, in list of the checkpoints of SQL Server Network Name resource. SQL Server Network Name is associated with clustered instance. Furthermore, updates of SQL Server Agent application configuration aren't spread to other cluster nodes when SQL Server resource group goes to the nodes.

The below registry subkey is used by SQL Server Agent:

HKEY_LOCAL_MACHINE\Software\Microsoft\Microsoft\SQL Server\<Instance ID of SQL Server that needs to be configured>\SQLServerAgent

How to Fix this Problem?

You can Recover MDF file in such cases by using the below steps:

• Click Start button and select Run.

• Type cmd, to open command prompt, and click OK button.

• Type cluster . resource /checkpoints and press Enter key.

• Check whether the below registry subkey comes out as a result:

HKEY_LOCAL_MACHINE\Software\Microsoft\Microsoft SQL Server\< SQL Server's Instance ID>\SQLServerAgent

• If you cannot see this registry subkey, type the underwritten command and press Enter key:
  cluster . resource /addcheckpoints:"HKEY_LOCAL_MACHINE\Software\Microsoft\Microsoft SQL Server\<SQL Server's Instance ID>\SQLServerAgent"

You should always backup your Windows registry before you proceed for this method. Improper editing of registry may cause serious problems and create needs of MDF Recovery solutions to retrieve data from SQL Server database.

You can successfully repair and restore your damaged Microsoft SQL Server database using effective third-party applications, known as MDF Repair software. They are incorporated with advanced scanning algorithms to carry out systematic scan of whole database and extract inaccessible data. The applications ensure safe and easy recovery with read-only conduct and interactive user interface.

SQL Recovery the most excellent SQL database recovery software ever made. The software is capable of repairing damaged database of Microsoft SQL Server 2008, 2005, and 2000. It restores all MDF file objects, such as tables, reports, forms, macros, stored procedures, and triggers.

Resource Taken From: http://www.programmersheaven.com/user/williumdavid/blog/4840-How-to-Fix-Missing-Checkpoint-For-Registry-Subkey-of-SQL-Server-Agent/