Datafile and MDF_MSSQL_DBCC8

Question

One of the database has MDF_MSSQL_DBCC8 file besides its own datafile. The user also noticed that some of the data was missing from the database. Not sure what to do with these files or how to correct the database.

Answer 1

That's not the common naming convention for database files, but they can be named as one like.

You can get the associated database with this query

select mf.name, mf.physical_name, db.name
from sys.master_files as mf
     inner join
     sys.databases as db
         on mf.database_id = db.database_id
order by db.name

Answer 2

Hi SahaSaha-5270,

MDF_MSSQL_DBCC files are the internal snapshot database generated for dbcc checkdb. The new MDF_MSSQL_DBCC files are deleted at the end of DBCC CHECKDB processing. If the operating system encounters an unexpected shutdown while the DBCC CHECKDB command is in progress, then these files will not be cleaned up. They will accumulate space, and potentially will prevent future DBCC CHECKDB executions from completing correctly. In that case, you can delete these new files after you confirm that there is no DBCC CHECKDB command currently being executed.
Please refer to What is .mdf_MSSQL_DBCC15 file which might help.

Best Regards,
Amelia

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Answer 3

Hi SahaSaha-5270,
Thanks for your reply.

How do I check if DBCC CHECKDB command is in progress.

Please try this:

SELECT  session_id ,
request_id ,
percent_complete ,
estimated_completion_time ,
DATEADD(ms,estimated_completion_time,GETDATE()) AS EstimatedEndTime,
start_time ,
status ,
command
FROM sys.dm_exec_requests
where command like '%DBCC%'

Best Regards,
Amelia

Answer 4

Two leftover DBCC files and user claiming data missing. Hmm, seems like there could be some trouble. Have you checked the SQL Server errorlog? If DBCC has run into trouble, this should appear here.