Following on from my previous post on boot pages and boot page corruption, I've been asked about file header pages - and I was already planning this post as the next in the series.

So what's a file header page? 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 and it will interpret all the fields for you, or you can use the DBCC FILEHEADER command, which does a better job. This is undocumented and unsupported, just like DBCC DBINFO 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.

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:

DBCC FILEHEADER ('FileHeaderTest', 1);
GO

FileId                : 1
LogicalName           : FileHeaderTest
BindingId             : D30AE3EF-14A6-47D5-B267-96F38238D882
FileGroup             : 1
Size                  : 152
MaxSize               : -1
MinSize               : 152
UserShrinkSize        : -1
Growth                : 128
BackupLSN             : 0
RedoStartLSN          : 0
FirstLSN              : 0
MaxLSN                : 0
FirstUpdateLSN        : 0
CreateLSN             : 0
SectorSize            : 512
RecoveryForkGUID      : 00000000-0000-0000-0000-000000000000
RecoveryForkLSN       : 0
DifferentialBaseLsn   : 19000000048800037
DifferentialBaseGuid  : 279A8EF4-4431-4CA5-8939-F613E5BC3033
Status                : 2
RestoreStatus         : 0
ReadOnlyLsn           : 0
ReadWriteLsn          : 0
MaxLsnBranchId        : 00000000-0000-0000-0000-000000000000
RedoTargetPointLsn    : 0
RedoTargetPointGuid   : 00000000-0000-0000-0000-000000000000
RestoreDiffBaseLsn    : 0
RestoreDiffBaseGuid   : 00000000-0000-0000-0000-000000000000
RestorePathOriginLsn  : 0
RestorePathOriginGuid : 00000000-0000-0000-0000-000000000000
OldestRestoredLsn     : 0

Lots of interesting stuff in here, such as:

• BindingId: used to make sure a file is really part of this database
• SectorSize: the disk sector size
• Status: what kind of file and what state is it in (e.g. 2 = regular disk file)
• Various sizes in number-of-8kb-pages (e.g. MaxSize of -1 means file growth is unlimited)
• Growth: the number of pages to grow the file by if the 0x100000 bit is NOT set in the Status field. If it is set, the Growth is in percent.

And you can watch things change. For instance, if I change the file growth to 10%:

ALTER DATABASE FileHeaderTest MODIFY FILE (NAME = FileHeaderTest, FILEGROWTH = 10%);
GO

And then dump the file header page contents again, the Status and Growth fields have changed to:

.
.
Growth                : 10
.
.
Status                : 1048578
.
.

So what if a file header page is corrupt? I corrupted the file header page of my database and then started up SQL Server.

USE FileHeaderTest;
GO

Msg 945, Level 14, State 2, Line 1
Database 'FileHeaderTest' cannot be opened due to inaccessible files or insufficient memory or disk space. See the SQL Server errorlog for details.

A couple of weeks ago I blogged about the three tracks of the SQL Server 2008 JumpStart course that SQLskills.com taught internally for Microsoft and some MVPs - see here for details. Well, the content is now available to download! Note that this was based on CTP-5 (November 2007 CTP) and there have been *lots* of behavioral changes since then (with more planned for CTP-6 Refresh and RTM), but if you want a high-level overview of a bunch of the features (albeit in bullet-point summaries on slides) then this is a good place to start.

For me, what's *REALLY* cool is that the site also has a downloadable VPC plus lab manuals for all of the AlwaysOn High-Availability hands-on labs that SQLskills.com wrote. We originally wrote these labs for SQL Server 2005 and I updated them all for CTP-5. The VPC has a long lab on each of the following:

• Database Snapshots
• Data Recovery and Preventative Techniques
• Instant Initialization
• Peer-to-Peer Replication (including the new Topology Wizard I blogged about here)
• Table and Index Partitioning
• Snapshot Isolation
• Online Operations
• Database Mirroring (including a demo I wrote of Automatic Page Repair, described here)
• Service Oriented Database Architecture

There is some great depth in each of these - Kimberly blogged more info about the exercises in each lab here. There's also another VPC image with some higher-level labs on a variety of 2008 features and written by a number of different people- including some labs on Policy-Based Management and Performance Data Collection that Kimberly wrote.

So - where can you get these from? Go to http://sqlserver2008jumpstart.microsofttraining.com/ and hit the Download link on the right-hand side. Register and then you can get to the materials. The AlwaysOn VPC image is Collection 2 at the bottom of the page, and you'll see all the slide decks as you scroll down the page.

Enjoy!