The Art of SQL Server FILESTREAM - Red Gate Software

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Chapter 7: FILESTREAM Database AdministrationChecking for database consistencyConsistency of the FILESTREAM data can be checked using DBCC CHECKDB for the entiredatabase, or DBCC CHECKTABLE to validate a single table. In Listing 7-15, we run DBCCCHECKTABLE to scan the table that we just corrupted by deleting the FILESTREAM datafile using Windows Explorer.DBCC CHECKTABLE('Items')/*DBCC results for 'sys.FILESTREAM_tombstone_2073058421'.There are 0 rows in 1 pages for object"sys.FILESTREAM_tombstone_2073058421".DBCC results for 'Items'.Msg 7904, Level 16, State 2, Line 1Table error: Cannot find the FILESTREAM file"00000015-0000005e-0004" for column ID 4 (column directoryID 4d8cb114-f573-490e-adfa-e4583889b836) in object ID 2105058535,index ID 0, partition ID 72057594038779904, page ID (1:157),slot ID 0.There are 2 rows in 1 pages for object "Items".CHECKTABLE found 0 allocation errors and 1 consistency errorsin table 'Items' (object ID 2105058535).repair_allow_data_loss is the minimum repair level for theerrors found by DBCC CHECKTABLE (NorthPole.dbo.Items).DBCC execution completed. If DBCC printed error messages, contactyour system administrator.*/Listing 7-15:Scanning the corrupted table.As expected, the DBCC CHECKTABLE command scanned the entire table and detected thata FILESTREAM data file is missing from the FILESTREAM data container.288
Fixing corrupted dataChapter 7: FILESTREAM Database AdministrationOne of the key features offered by FILESTREAM is consistency between FILESTREAMdata and relational data. We just deleted a FILESTREAM data file directly (outside SQLServer) and so lost the consistency of data. The only way to fix this is either by deletingthe row that contains the FILESTREAM data file (recommended), or by adding the lost fileback to the FILESTREAM data container.If you do not want to lose the relational data, you could fix the corruption by copyingback the correct file directly into the FILESTREAM data container. This requires that youhave the ability to locate a backup copy somewhere, possibly by restoring from a backup.SQL Server allows you to query the relational data even though the FILESTREAM data iscorrupted, which may help you to identify which data value is missing. Note that the filename of the new file must be the same; the file name and location can be identified fromthe DBCC error message.If you cannot locate a copy of the missing or corrupt file, you can put a dummy file withthe expected file name into the FILESTREAM data folder, and this will "fix" the corruptionso that you do not have to delete the relational data (which may be hard to get back). Forexample, if your table stores the avatar of users and you lost the image of one record dueto a mistake, you could put an anonymous image file into the FILESTREAM data folder.To use a dummy file, locate an existing file or create a new file that is of the same type asthe missing file. Copy the dummy file to the FILESTREAM data container and rename itto match the name of the missing file (as reported by DBCC CHECKDB). Having done so,rerun DBCC CHECKDB or DBCC CHECKTABLE, and you will see that the corruption is fixed.If you can tolerate some degree of data loss, then the alternative solution is to deletethe row from the table to make the data consistent; we can do this by running DBCCCHECKDB with repair_allow_data_loss, which is about as scary as it sounds; we'reabout to lose some data! In this case, it will delete the associated row(s) from the table andrestore the consistency of the data.289
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DBA HandbooksThe Art ofSQL Server F
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Copyright June 2012ISBN 978-1-90643
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Updating and deleting FILESTREAM da
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Creating the stored procedure to fe
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File Backups and Piecemeal Restores
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Setting Up the Server for FileTable
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Using SSMS to check that FILESTREAM
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Sven AeltermanSven Aelterman is a l
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Finding time for writing such a len
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IntroductionWhen I first started my
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The secondary audience for this boo
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Chapter 1: Storing and ManagingUnst
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Chapter 1: Storing and Managing Uns
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Setting the access levelChapter 1:
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Data usage patternsChapter 1: Stori
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Chapter 2: Getting Started with FIL
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Chapter 3: Accessing FILESTREAMData
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Chapter 4: FILESTREAM with EntityFr
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Chapter 5: FILESTREAM with ASP.NETa
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Chapter 6: FILESTREAM with SSIS and
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Chapter 9: Investigating FILESTREAM
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Chapter 10: Integrating FILESTREAMw
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Chapter 10: Integrating FILESTREAM
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Chapter 11: FileTableThe addition o
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Chapter 11: FileTableColumn Namestr
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Chapter 11: FileTableColumn Nameis_
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Chapter 11: FileTableUSE NorthPoleG
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Chapter 11: FileTableMore on using
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Chapter 11: FileTableFigure 11-1:Se
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Chapter 11: FileTableperformance wh
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Chapter 11: FileTableany files or f
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Chapter 11: FileTable-- If the 'Nor
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Chapter 11: FileTableBy default, th
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Chapter 11: FileTableIt is possible
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Chapter 11: FileTableFigure 11-4:Ch
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Chapter 11: FileTableFurthermore, i
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Chapter 11: FileTableCreating folde
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Chapter 11: FileTableAdding rows us
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Chapter 11: FileTable-- Find the pa
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Chapter 11: FileTable-- Insert a ne
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Chapter 11: FileTablestring SqlText
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Chapter 11: FileTableAs a best prac
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Chapter 11: FileTableSELECT file_st
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Chapter 11: FileTableListing 11-29
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Chapter 11: FileTableInvestigating
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Chapter 12: Planning, Configuration
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Appendix A: Configuring FILESTREAMo
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Appendix A: Configuring FILESTREAM
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