{"id":1036,"date":"2008-07-25T14:10:50","date_gmt":"2008-07-25T14:10:50","guid":{"rendered":"\/blogs\/paul\/post\/Search-Engine-QA-21-File-header-pages-and-file-header-corruption.aspx"},"modified":"2021-12-29T14:49:23","modified_gmt":"2021-12-29T22:49:23","slug":"search-engine-qa-21-file-header-pages-and-file-header-corruption","status":"publish","type":"post","link":"https:\/\/www.sqlskills.com\/blogs\/paul\/search-engine-qa-21-file-header-pages-and-file-header-corruption\/","title":{"rendered":"Search Engine Q&A #21: File header pages, and file header corruption"},"content":{"rendered":"

Following on from my previous post on boot pages and boot page corruption<\/a>, I’ve been asked about file header pages – and I was already planning this post as the next in the series.<\/p>\n

So what’s a file header page<\/em>? Every data file in a database has the very first 8kb page (i.e. page 0 in the file) set aside as the place to store all the metadata info about the file. As with the boot page, you can look at the contents with DBCC PAGE<\/span> and it will interpret all the fields for you, or you can use the DBCC FILEHEADER<\/span> command, which does a better job. This is undocumented and unsupported, just like DBCC DBINFO<\/span> for looking at the database boot page, but it’s been discussed and posted about on the Internet before so it’s existence is no secret.<\/p>\n

The command take a database name or database ID plus the file ID to dump. Here I’ve created a database called FileHeaderTest and used SSMS with results-to-text, plus a bunch of editing of the results to make it blog-able:<\/p>\n

DBCC<\/span> FILEHEADER <\/span>(<\/span>‘FileHeaderTest’<\/span>,<\/span> 1<\/span>);
\n<\/span><\/span>GO<\/span><\/span><\/p>\n

FileId\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 1
\nLogicalName\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : FileHeaderTest
\nBindingId\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : D30AE3EF-14A6-47D5-B267-96F38238D882
\nFileGroup\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 1
\nSize\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 152
\nMaxSize\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : -1
\nMinSize\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 152
\nUserShrinkSize\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : -1
\nGrowth\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 128
\nBackupLSN\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nRedoStartLSN\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nFirstLSN\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nMaxLSN\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nFirstUpdateLSN\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nCreateLSN\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nSectorSize\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 512
\nRecoveryForkGUID\u00a0\u00a0\u00a0\u00a0\u00a0 : 00000000-0000-0000-0000-000000000000
\nRecoveryForkLSN\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nDifferentialBaseLsn\u00a0\u00a0 : 19000000048800037
\nDifferentialBaseGuid\u00a0 : 279A8EF4-4431-4CA5-8939-F613E5BC3033
\nStatus\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 2
\nRestoreStatus\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nReadOnlyLsn\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nReadWriteLsn\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 0
\nMaxLsnBranchId\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 : 00000000-0000-0000-0000-000000000000
\nRedoTargetPointLsn\u00a0\u00a0\u00a0 : 0
\nRedoTargetPointGuid\u00a0\u00a0 : 00000000-0000-0000-0000-000000000000
\nRestoreDiffBaseLsn\u00a0\u00a0\u00a0 : 0
\nRestoreDiffBaseGuid\u00a0\u00a0 : 00000000-0000-0000-0000-000000000000
\nRestorePathOriginLsn\u00a0 : 0
\nRestorePathOriginGuid : 00000000-0000-0000-0000-000000000000
\nOldestRestoredLsn\u00a0\u00a0\u00a0\u00a0 : 0<\/span><\/span><\/p><\/blockquote>\n

Lots of interesting stuff in here, such as:<\/p>\n