How to Remove the “Chain Sequence Numbers are Out of Order” Error Message?

The IAM or the Index Allocation Map page in the MS SQL Server database is the metadata entry that maps extends in the 4 GB part of the database file. Each IAM number has a sequence number that acts as the exact position in the IAM chain. But sometimes one may encounter the "Chain sequence numbers are out of order" message and an error message like the following:

"Chain sequence numbers are out of order in IAM chain for object ID O_ID, index ID I_ID. Page P_ID1 sequence number SEQUENCE1 points to page P_ID2 sequence number SEQUENCE2."

The most common reason for the occurrence of the error message is metadata corruption which means that the sequence numbers of the IAM pages has got corrupt. Due to the corruption, the data stored in the database becomes inaccessible and one cannot access the data for the various purposes. Such a situation can be encountered due to a number of software or hardware factors.

To get rid of the chain sequence numbers are out of order message one needs to follow a few simple steps. You need to find out the exact reason for the occurrence of the error due to the corruption of the sequence numbers of the IAM pages. To make out whether the error is the result of hardware problems you need to run hardware diagnostics and swap the different hardware components and find the faulty hardware component. For other issues causing the error you can run the DBCC CHECKDB command.

But if the corruption is severe, then the command would not help. In such a situation, getting access to the data would be impossible without the help of an efficient and reliable third party MDF repair tool that can repair the database and retrieve all the database objects. To get rid of the corruption one can format the system and then reinstall the application one more time but not before backing up the data stored in the databases.