-> I tried attaching a MDF file without LDF file using below command and it worked fine,
-> The database JBSWiki looks fine.
-> I tried executing below query and got an error,
select * from Table1
Msg 824, Level 24, State 2, Line 1
SQL Server detected a logical consistency-based I/O error: incorrect checksum (expected: 0x78812100; actual: 0x7881211c). It occurred during a read of page (1:320) in database ID 6 at offset 0x00000000280000 in file ‘c:\temp\JBSwiki.mdf’. Additional messages in the SQL Server error log or operating system error log may provide more detail. This is a severe error condition that threatens database integrity and must be corrected immediately. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.
-> It is clear from the message that the database is corrupted. Let me execute a DBCC Checkdb and validate the results,
use [master] GO dbcc checkdb ('JBSWiki')
Msg 8939, Level 16, State 98, Line 3
Table error: Object ID 677577452, index ID 1, partition ID 72057594043760640, alloc unit ID 72057594050248704 (type In-row data), page (1:320). Test (IS_OFF (BUF_IOERR, pBUF->bstat)) failed. Values are 133129 and -4.
Msg 8928, Level 16, State 1, Line 3
Object ID 677577452, index ID 1, partition ID 72057594043760640, alloc unit ID 72057594050248704 (type In-row data): Page (1:320) could not be processed. See other errors for details.
Msg 8980, Level 16, State 1, Line 3
Table error: Object ID 677577452, index ID 1, partition ID 72057594043760640, alloc unit ID 72057594050248704 (type In-row data). Index node page (0:0), slot 0 refers to child page (1:320) and previous child (0:0), but they were not encountered.
CHECKDB found 0 allocation errors and 3 consistency errors in database ‘JBSWiki’.
repair_allow_data_loss is the minimum repair level for the errors found by DBCC CHECKDB (JBSWiki).
-> From the error message we can see that the corruption is on Object id 677577452 and the minimum repair level for correcting this issue using DBCC checkdb is repair_allow_data_loss. This means there will be data loss.
-> Lets check what object id 677577452 is using below query,
use [JBSWiki] GO select object_name(677577452 ) as 'Corrupted Table Name'
-> So we know that there is an issue on Table1 object and from the DBCC Checkdb results we can see that page 320 in File id 1 is experiencing issue. Data loss is not an option in this case.
-> The only option left is to restore the database with a valid backup. But the bad news is that there are no backups.
-> SQL Server Database recovery tools is something we can check as an option. In my case, I tried “Stellar Repair for MS SQL“.
-> Before using Stellar Repair for MS SQL tool, it is better to backup the MDF and LDF file for safety.
-> Once done make another copy of the files to use it with Stellar Repair for MS SQL tool. In my case I have placed the file in location F:\Debug,
-> Open “Stellar Repair for MS SQL” and click on “Select database”,
-> Select the corrupted MDF file and click on Repair,
-> Repair completed,
-> Once repaired, Click on Save,
-> Processing this new database is going to take time depending on the database size. The time spent is definitely worth it, as I was able to recover the whole database.
-> Once the database is recovered. Do thorough testing and make sure the database looks alright.
-> I executed DBCC CHECKDB on the new database recovered by Stellar Repair for MS SQL and it came out clean.
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