DBCC CHECKDB scalability and performance benchmarking on SSDs

Back in February I ran a bunch of performance tests of DBCC CHECKDB on SSDs, to evaluate the effects of degree-of-parallelism (DOP) and various options and traceflags, and now I’m finally getting around to presenting the results. Make sure to also read the recent┬ápost where I talk about the detrimental effect of computed-column indexes on […]

The pros and cons of trace flags

If I told you about an undocumented mod you could make to your car's brakes to make them more efficient, would you try it? What if a random mechanic told you? What if someone who's an expert in your make and model of car told you? What if the car manufacturer asked you to try it […]

Survey: what’s your comfort level with trace flags in production?

After finishing the salary survey I was kicking around ideas for the next one and thought about one of the sessions I presented at SQL Connections in Spring this year and Fall last year about undocumented tips and tricks (just the tip of the iceberg!). In that presentation I covered a bunch of trace flags […]

A SQL Server DBA myth a day: (30/30) backup myths

(Look in the Misconceptions blog category for the rest of the month’s posts and check out the 60-page PDF with all the myths and misconceptions blog posts collected together when you join our Insider list, plus my online Myths and Misconceptions training course on Pluralsight.) The month is finally over so time for the grand […]

Turning off the ghost cleanup task for a performance gain

I've blogged about ghost records and the ghost cleanup task a couple of time before (the only place it is really explained AFAIK), but one of my fellow MVPs was asking me some questions about it today for a customer of theirs and couldn't find the trace flag to turn it off. My previous blog […]

Misconceptions around TF 1118

There’s been a recent flurry of confusion and misconceptions about trace flag 1118 in SQL Server 2008. This trace flag switches allocations in tempdb from single-page at a time for the first 8 pages, to immediately allocate an extent (8 pages). It’s used to help alleviate allocation bitmap contention in tempdb under a heavy load […]

Fed up with BACKUP success messages bloating your error logs?

There’s a well known problem that every time a backup operation succeeds a message is written into the error log and Windows event log. If you’re taking very frequent log backups (say every 5 minutes) of multiple databases, that’s a significant amount of clutter in the logs. Well – now there’s a fix! Kevin Farlee, […]

BACKUP LOG WITH NO_LOG – use, abuse, and undocumented trace flags to stop it

This has come up several times over the last few days, and is something that Kimberly and I discuss (and deplore) when we lecture – the use of BACKUP LOG WITH NO_LOG (or TRUNCATE_ONLY – they’re synonymous) to allow log truncation. How is it used? The common use is when the transaction log grows to […]

SQL Server 2008: Performance boost for Database Mirroring

As I mentioned in a previous post, one of the new features for database mirroring in SQL Server 2008 is log stream compression. There’s a good explanation of what this is (along with some example workloads and performance graphs) on the SQL Customer Advisory Team blog so I’m not going to duplicate all that here. Basically, the […]

SQL Server 2008: Lock escalation changes

SQL Server supports lock escalation – when the server decides to move from a large number of row or page locks on an object to a table-level lock. Sunil Agarwal posted a great description of lock escalation in SQL Server 2005 on the Storage Engine blog so I won’t repeat it all here. The problem with […]

Inside the Storage Engine: Using DBCC PAGE and DBCC IND to find out if page splits ever roll back

Time for the first post in the Inside the Storage Engine series. I’m going to focus on SQL Server 2005 in this series and I’ll point out major differences between 2005 and previous versions. Please drop me a line if there’s something you’d like to see explained and demo’d. Before jumping into how things work, […]

SQL Server 2008: Automatic Page Repair with Database Mirroring

One of the hottest features in SQL Server 2005 is database mirroring, and it's helped many companies implement successful and relatively inexpensive high-availability strategies. In SQL Server 2008, Database Mirroring has been enhanced in several ways – one of which is the ability to automatically repair corrupt pages! This feature is based on the fact that the […]

How to tell if the IO subsystem is causing corruptions?

  One of the comments I received recently is below: Hi Paul, If the corruption happens to be related to I/O Erros and there is nothing in the Event log or anywhere that points to I/O related issues, is there any Trace flag that we can enable when performing checkdb or checktable operations that can […]