Category Archives: Compression

How Do *YOU* Measure SmartScans?

With SmartScans being the most important (and most unique) performance feature for Exadata, it’s incredibly useful to measure how well you’re making use of it.

But how?

There are a number of ways you can measure this, but none of these seem to be the DEFINITIVE method to do so.  Instead, it’s probably a good idea to more than one formula, if not all, to get a good idea of our SmartScan usage.

Why are there multiple formulas?  Because the existing database metrics don’t quite capture what we’re looking to measure.  For instance:

  • physical read total bytes‘ –  is all the data including compressed data AND SmartScan-ineligible data.
  • cell physical IO interconnect bytes‘  –  includes the writes (multiplied due to ASM mirroring) AND the reads.
  • cell IO uncompressed bytes‘  –  is the data volume for predicate offloading AFTER the Storage Index filtering and any decompression
  • cell physical IO interconnect bytes returned by smart scan‘  –  includes uncompressed data.

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My Collaborate IOUG 2015 Abstract

I will be presenting DBA 3.0 or “How to Become a Real-World Exadata DBA” at Collaborate 2015 – IOUG’s annual user conference – from April 12th to 16th at the Mandalay Bay Resort and Casino in Las Vegas. I submitted this as my abstract:

“DBA resources are more scarce than ever before and it can be very difficult to allocate time on anything but keeping the lights on – even when an organization has made a (substantial) hardware investment in Exadata.

However, if Exadata is treated like any other Oracle database, the promised “extreme performance” will likely be very underwhelming to developers, users and managers and can become unwieldy for DBAs to support.

On the other hand, when an organization configures and supports Exadata properly, they can realize exponential performance improvements in key IT infrastructure, can facilitate better business decisions and may actually reduce infrastructure costs.

The customer has bought a sports car – but might not realize that they haven’t taken it out of second gear (yet).

I will talk about the evolution of Exadata and then get into the “nuts and bolts” of how to support a high-performance Exadata environment as a Production DBA.

I will discuss how to get performance improvements of up to 20x, what NOT to do as an Exadata DBA and how Exadata can become the foundation of your organization’s high-performance enterprise infrastructure.”

I hope to see you in Las Vegas!

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OLTP Compression vs. Single Row Inserts

Day 3 of my new gig and I hit a rare bug with OLTP compression (new in 11g) while executing single-row INSERT statements.

Luckily, my new colleagues are excellent notekeepers as well as excellent DBAs – they had seen it before and quickly found the workaround they’d used previously. Basically, the session got hung trying to find free space in which to put the new block.

And, yes, this was on an Exadata box, so I was able to recommend EHCC as an alternative to OLTP compression 🙂

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