Several server users face multiple errors while accessing database on their machine. However, general cause of these errors is corruption related problem. One such issue is corruption in clustered index due to which the data becomes inaccessible for end users. Users will not be able to access database and hence, face a problem while working with the server.
Database is the most important integral part for every organization and a condition may occur in which users will have to start their work from beginning, which will consume a lot of time & efforts. Therefore, there exists a need for a solution by which users can repair clustered index, as a result of which they could not face the data loss situation. In this blog, we are going to learn about all the possible ways to repair clustered index along with a short intro about clustered index and reasons behind corruption of it.
What is Clustered Index in SQL Server?
In SQL server, there exists an index that increases the performance of queries by reducing the visited and scanned number of database data pages. Moreover, there exists a special index called clustered index, which sorts the record stored in the table. This index is one for one table i.e., a table can have only one clustered index within it. The structure of clustered index is built in such a way that its leaf nodes contains the data pages.
Database users are recommended to create multiple non-clustered index in order to create database backup because each table can have more than one non-clustered index. Hence, if in case the clustered index gets corrupted, then they can restore the data from backup file. When clustered index gets corrupted at that time the following error message appears:
Server: Msg 1902, Level 16, State 3, Line 1
Cannot create more than one clustered index on table
'Table Name'. Drop the existing clustered index
'Clustered Index Name' before creating another.
Cause for Corruption in Clustered Index:
There are very common reasons due to which these indexes gets corrupted, as such there does not exists any special reasons due to which this index corruption takes place. Some of the common reasons are highlighted below:
- Different virus attacks harms the SQL server database file
- Improper management system of the server’s memory
- Irrelevant changes made in default server settings
- Abnormal shutting down operation of the server
NOTE: When corruption occurs, more than one clustered index appear in database, which is actually the abnormal behavior of the server. The corruption is caused either on one index page or all the database pages.
Techniques To Repair Clustered Index in SQL Server
- Repairing With The Help of Backup File
- Repairing Indexes With Help of DBCC CHECKDB command
- Repairing With Help of a Recovery Software
If you have created a backup of clustered index, then the very first and relevant approach is to restore working copy of the database. Well, this approach is very useful when modifications made in the database is less. If the corruption is only on an individual page, then you can easily repair it by page level restoration. In case, multiple pages gets corrupted use database level restoration.
You can repair less corrupted database files and rebuild data from it. Following command will help you to rebuild data from corrupted files:
DBCC CHECKDB ('DB_Name', REPAIR_REBUILD)
In order to allow data loss at the time of repairing indexes and fixing all errors, you can use following command
DBCC CHECKDB ('DB_Name', REPAIR_ALLOW_DATA_LOSS)
Since the database files gets corrupted, which causes numerous errors in the server therefore, to repair such files and restore data from them, one should go for a third-party utilities that are easily available on internet. One such tool is SQL recovery software that recover SQL database and export them into SQL server database or server compatible scripts. Moreover, it also recovers deleted SQL server database table that may be useful for end users.
Until now we have studied all possible tricks to repair clustered index of SQL server. If non-clustered index is available with user, then the first approach is suitable for repairing index. However, if backup is not available, then it is advised to end users to use third party SQL recovery software.