July 2009 - Posts

• Transaction Isolation / Dirty Reads / Deadlocks Demo

  I have just given a talk with my group at work on the basics of transaction isolation, dirty reads (nolock) and deadlocks, just as a way to get eveyone on the same page about the tradeoffs between concurrency on a busy transactional system and accuracy Read More... Posted Wednesday, July 29, 2009 4:44 PM by merrillaldrich | 4 Comments Filed under: Deadlocks, Locking, NoLock

• SAN Disk Array Performance: Beware LUN Concatenation

  I'd like to pass along a couple of tips for those new to using SAN storage for SQL Server. SAN Storage is quite expensive, and doubly so if your storage doesn't deliver on the performance front. SAN disk arrays are not magic, and sadly they don't just Read More... Posted Sunday, July 26, 2009 5:17 PM by merrillaldrich | 2 Comments Filed under: performance, san

• Flow control in T-SQL Scripts

  When many people, including me, began their early T-SQL efforts, the magic two letter GO statement was a bit mysterious. What was that for? Was it just decoration sprinkled through your scripts? What’s the difference when two SQL statements are separated Read More... Posted Friday, July 24, 2009 9:17 AM by merrillaldrich | 15 Comments Filed under: errors, flow control, transactions

• Hole in your Backup Sequence?

  I have been stung by this scenario a few times, using SQL Server's typical sliding window to remove old backup files: The backup disk is nearly full Full Backups are the largest kind, typically, and the Fulls start to fail first if there's a lack of disk Read More... Posted Tuesday, July 21, 2009 9:08 AM by merrillaldrich | 3 Comments Filed under: backup, CLR, xp_cmdshell Attachment(s): BackupDeleteCodeSample.txt

• Random Join, STAT

  I've been tinkering with a little puzzle, mainly for fun: suppose you need to generate a large number of "mock" names either for generating test data or for masking data that's restored from a production system into a test environment. For this task I Read More... Posted Monday, July 20, 2009 10:27 AM by merrillaldrich | 1 Comments Filed under: cross join, random ordering

• New Blog

  It's a great time to be a DBA, of any flavor. I am a SQL Server DBA in the Seattle area, and I love what I do. The SQL Server online community is rich and varied, with some of the smartest and most generous IT people you'll find, and the product itself Read More... Posted Sunday, July 19, 2009 7:17 PM by merrillaldrich | 0 Comments