An IAM (Index Allocation Map) page in MS SQL Server database is a metadata entry that plans the extents in a 4GB part of database file. This database file is used by three types of allocation units they are IN_ROW_DATA, LOB_DATA, and ROW_OVERFLOW_DATA. An IAM page includes a header to indicate the beginning range of Extents mapped by that particular IAM page. Moreover, every IAM page contains a sequence number, which acts as its exact position within the IAM chain. Corruption in the sequence numbers primarily results the inaccessibility of records stored in the database. In such situations, if you want to access your data, then you need to restore the data from an updated backup. However, if no backup is available or backup it self’s corrupted, then you need to use powerful SQL database recovery software.
Consider a practical scenario, where you meet the below error message when you try to access your database:
“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.”
Your database records become inaccessible after getting the above error message pops up. The same error message reappears every time when you try to access your database records.
The primary reason for the occurrence of the above error is metadata corruption i.e the sequence numbers of the IAM pages is corrupted.
For complete troubleshooting of the above error message, you need to analyze the exact reason for the corruption of metadata (sequence numbers of IAM pages). If the corruption is due to hardware failure, then change the hardware component. However, in case of software corruption, run DBCC CHECKDB command – with appropriate repair clause – to repair the database.
DBCC CHECKDB command allows complete repair in most cases. But, if the command fails, then the only option is to use advanced SQL Recovery software. Such SQL Database Recovery applications employ high end scanning mechanisms to repair the database.
Consider a practical scenario, where you meet the below error message when you try to access your database:
“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.”
Your database records become inaccessible after getting the above error message pops up. The same error message reappears every time when you try to access your database records.
The primary reason for the occurrence of the above error is metadata corruption i.e the sequence numbers of the IAM pages is corrupted.
For complete troubleshooting of the above error message, you need to analyze the exact reason for the corruption of metadata (sequence numbers of IAM pages). If the corruption is due to hardware failure, then change the hardware component. However, in case of software corruption, run DBCC CHECKDB command – with appropriate repair clause – to repair the database.
DBCC CHECKDB command allows complete repair in most cases. But, if the command fails, then the only option is to use advanced SQL Recovery software. Such SQL Database Recovery applications employ high end scanning mechanisms to repair the database.
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