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  • Blog Post: CHECKDB (Part 8): Can repair fix everything?

    I was teaching at a Microsoft-internal class last week and there was a discussion on what corruptions can't be repaired using DBCC. At the same time, several threads popped up on forums and newsgroups with people hitting some of this unrepairable corruptions so I thought that would make a good topic...
  • Blog Post: More undocumented fun: DBCC IND, DBCC PAGE, and off-row columns

    (Final blog post of the year for me. Its been a bit of a wild ride the last 6 months - 7 TechEds on 3 continents, 46 blog posts and some major life changes - but now things have calmed down and I should be back to more regular posting in 2007. Tomorrow I fly out to Wakatobi in Indonesia to go diving...
  • Blog Post: When can allocation order scans be used?

    I know this is jumping the gun a little as I haven't made it this far in my series on fragmentation , but this came up in a chalk-talk I did yesterday at TechEd Developers in Barcelona and is worth blogging about. You'd expect a select * from mytable query on a table with a clustered index to use...
  • Blog Post: Fragmentation (part 4): what are heaps?

    Ok - really catching up with the various blog post series I started back in June/July - time to bang out the next few posts in the series on index fragmentation. Remember I'm starting from first principles and covering What are records? What are pages? What are extents? What is a heap...
  • Blog Post: Don't try this at home kids... (data recovery using DBCC PAGE)

    Time to cough up a real-life data recovery scenario to temporarily stop those people who badger me relentlessly for scenarios... We have a situation currently with a customer who managed to delete all their data during a SAN reconfig and then found out that their tape backups hadn't been working properly...
  • Blog Post: Poking about with DBCC PAGE (Part 1 of ?)

    (It's been a while since I last posted - summer fun's been in the way obviously and I've been busy picking up some new and exciting (for me) SQL skills, partially to help with four upcoming TechEds I'll be doing in China and Hong Kong. The posting frequency should increase towards the end of the week...
  • Blog Post: Under the covers: GAM, SGAM, and PFS pages

    (Been a week or so since the last post but I haven't burnt out with blogging yet - I was on vacation over the July 4th weekend and totally offline in and around a small town called Pullman in south-eastern Washington.) In a previous post I described extents, and in another previous post a while...
  • Blog Post: Why is the NULL bitmap in a record an optimization?

    I've had some questions sent in comments and I wanted to reply to some of them using a post so others who aren't subscribed to the comment sections can see the answers. Wesley Backelant said: I was wondering what exactly you mean by "this allows an optimization when reading...
  • Blog Post: Fragmentation (part 3): What are extents?

    (Ok - another flight - another blog post. This time its Boston back to Seattle. The three of us who'd come over for the training course upgraded to 1st Class on Alaska for the flight back (great value at $100 for a 6-hour flight) and so there's oodles of room for laptops, newspapers, and long legs) ...
  • Blog Post: Under the covers: IAM chains and allocation units in SQL Server 2005

    (I'm sitting here in Seattle airport at 7am on Sunday waiting to catch the same flight to Boston that I caught two weeks ago. Instead of TechEd, this time I'm going to a training course at MIT. I'd enjoy the air travel a lot more with a bigger gap in between the flights. At least I got an aisle seat...
  • Blog Post: Fragmentation (part 2): What are pages?

    (Boston continues its reputation - with me at least - for great seafood - calamari and pan-seared fresh halibut this evening. Yum! I was tempted to get on the T - Boston's subway system - and see what's happening downtown but with no jacket I'd get wet. So, instead I'll be boring and geeky and write...
  • Blog Post: Under the covers: IAM chains in SQL Server 2000

    I've reached a point in my various ramblings where I need to do some glossary work. First up is an explanation of IAM chains. This will be in two parts, detailing how they're used in SQL Server 2000 and then in 2005. (Probably tomorrow as the sun's shining and I want to play with my tractor once the...
  • Blog Post: Fragmentation (part 1): What are records?

    This blogging thing sucks you in, doesn't it? Not content with having an ongoing series on disaster recovery and CHECKDB (with another 6 and 25 more posts planned respectively), I'm starting a new series on fragmentation. This will begin from first principles and work up, in approximately 18 posts over...
  • Blog Post: How to use DBCC PAGE

    Yes, finally I come clean and tell all. It's an open secret that there's an undocumented DBCC command called DBCC PAGE that you can use to look at the contents of database pages. I've recommended in forum postings that people use it and Product Support also asks customers to use it during various investigations...
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