Thursday, 4 October 2012

Book Review - Brad's Guide to Maintenance Plans

Or to give it its full title:
Brad's Sure Guide to SQL Server Maintenance Plans (Dba Handbooks)
by Brad M McGehee

An exhaustive haul through the various options that Microsoft provide for maintenance.  Brad spends a lot of time talking about the Wizard, much of that time warning against it!  He is wary of the wizard, in part because it could lead the unwary to ticking every box and thus doing unnecessary and even damaging stuff. Ticking Rebuild and Reorganise, for example - it just makes your plan take twice as long. If you Rebuild, then do an unnecessary Update Statistics, the update can screw up the statistics that the rebuild created and hit performance as well as wasting time.

I've never used the wizard myself - the SSIS-style drag and drop interface in the plan designer is so easy to use that I don't see the need. Brad also recommends using T-SQL or Powershell scripts for more complex maintenance. In fact he recommends this on average once per chapter, so it tends to get a little tedious.

To my mind, this leaves a lot of middle ground where the simplicity of the graphic maintenance plan designer does the job neatly and effectively. Want to take a backup? Just pick the backup task, spend a few moments telling it what to backup and where to, and then schedule it to run at a convenient time. Job done! Why write the code when the plan can do it for you?

Here's why - you can rebuild indexes, or reorganise indexes - but best practice is probably to read the fragmentation level of each one and then decide whether to rebuild, reorganise or leave alone. Especially on large databases, especially if you have a narrow maintenance window, you don't want to do an unnecessary rebuild. For this your best bet is a custom script.

But for most stuff the maintenance plan is fine. Brad reminds me of all the things I should be doing - like the history clean up task. Have I scheduled this? Probably not everywhere - note to self - go and check. And he explains very well the point of multiple sub-plans which I hadn't grasped before.

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