We’re Gonna Need a Bigger TEMP Tablespace

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It’s one of the most iconic scenes in American film – Roy Schneider’s character is chumming the water and sees the shark they are hunting. The massive size of the fish causes him to comment, “We’re gonna need a bigger boat!” It’s shark week, and I was struggling with inspiration for blog posts, so apologies if this metaphor is stretched beyond your imagination.

When Oracle (and SQL Server) need to do some expensive math operations, primarily SORTS, it needs a lot of disk space. When you want to join or order data, the database engine gets to do all the low-level yucky math stuff that you ignored in college (or at least I did). Instead of going to the OS for disk space to use this, the database has its own TEMP tablespace. In Oracle you can even have multiple tablespaces set aside for TEMP operations. But my questions are, ‘How much is enough?’ and ‘How much is too much?’

Wait, why is this bad?

I had never really considered having too much of anything as a problem before, but an offhand tweet last week by @erinstellato gave me pause. My current database has a 5+GB TEMP tablespace. The image it runs on only has 30GB of space and runs pretty full most of the time. So maybe my boat is really way too big? Or, maybe I can get greedy and steal back some of the space for my OS.

Instead of researching and finding out the best way to determine TEMP size, I’m just going to re-size this to 2GB and see what happens. I’ll wait and watch for

ORA-01652: unable to extend temp segment by string in tablespace string

I’ve additionally enabled auto-extend with 512MB increments.

How Do I Properly Size My TEMP Tablespace?

Is there a magic rule or ratio based on the size of your database or the number of transactions or users running amok in your system? Back in the day when I was managing customer databases, we had a script to build the database — which included TEMP — and then going forward we would just add space as necessary. Is this really the best way? I’m guessing not. So let’s jump to the innerwebs to see what the experts have to say!

It's official - You Suck at Google

  • Creation and Maintenance of TEMP (Oracle Docs) – good stuff, but nothing about sizing guidelines

And that’s all I could really find. Multiple Google’s on ‘sizing recommendations’ and ‘how to size’ really didn’t give me much. So I’m waiting for real production DBAs and other people smarter than me to share their thoughts here.

I’m also happy to learn more about sizing TEMPDB too if you’re a SQL Server type!

I’ll be happy to report back on the ‘magic number’ I end up with on my own personal Oracle 11gR2 database. Hopefully I come up with that number based on trial and error or science – and not on guessing. But I’ll be happy with a number that doesn’t starve the OS or the database. I think a lot of folks really only care about the end result and not how they got there. Is that bad when it comes to managing TEMP?

I found a few good links for stories and advice around being sure to tune your queries and having proper stats on your objects so you don’t slam TEMP. But how do you know when you’ve reached the limit of database tuning? Or

Is Your Server So Big You Can Afford to Throw Tons of Space at TEMP and Not Worry About It?

8/3/2011 Update
Enkitec consultant and Oracle expert Kellyn Pot’Vin did more than share a link, she authored a topic on the subject! Here it is in all its glory!

Warp Speed with Temp Tablespace Groups

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