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About index range scans, disk re-reads and how your new car can go 600 miles per hour!

Despite the title, this is actually a technical post about Oracle, disk I/O and Exadata & Oracle In-Memory Database Option performance. Read on :)

If a car dealer tells you that this fancy new car on display goes 10 times (or 100 or 1000) faster than any of your previous ones, then either the salesman is lying or this new car is doing something radically different from all the old ones. You don’t just get orders of magnitude performance improvements by making small changes.

Our take on the Oracle Database 12c In-Memory Option

Enkitec folks have been beta testing the Oracle Database 12c In-Memory Option over the past months and recently the Oracle guys interviewed Kerry OsborneCary Millsap and me to get our opinions. In short, this thing rocks!

Combining Bloom Filter Offloading and Storage Indexes on Exadata

Here’s a little known feature of Exadata – you can use a Bloom filter computed from a join column of a table to skip disk I/Os against another table it is joined to. This not the same as the Bloom filtering of the datablock contents in Exadata storage cells, but rather avoiding reading in some storage regions from the disks completely.

Enkitec + Accenture = Even More Awesomeness!

Enkitec is the best consulting firm for hands on implementation, running and troubleshooting your Oracle based systems, especially the engineered systems like Exadata. We have a truly awesome group of people here; many are the best in their field (just look at the list!!!).

This is why I am here.

What the heck are the /dev/shm/JOXSHM_EXT_x files on Linux?

There was an interesting question in Oracle-L about the JOXSHM_EXT_* files in /dev/shm directory on Linux. Basically something like this:

Oracle Memory Troubleshooting, Part 4: Drilling down into PGA memory usage with V$PROCESS_MEMORY_DETAIL

If you haven’t read them – here are the previous articles in Oracle memory troubleshooting series: Part 1Part 2,

Slides of my previous presentations

Here are the slides of some of my previous presentations (that I haven’t made public yet, other than delivering these at conferences and training sessions):

Scripts and Tools That Make Your Life Easier and Help to Troubleshoot Better:

  • I delivered this presentation at the Hotsos Symposium Training Day in year 2010:

 

Troubleshooting Complex Performance Issues – Part1:

 

Troubleshooting Complex Performance Issues – Part2

 

Where does the Exadata storage() predicate come from?

On Exadata (or when setting cell_offload_plan_display = always on non-Exadata) you may see the storage() predicate in addition to the usual access() and filter() predicates in an execution plan:

SQL> SELECT * FROM dual WHERE dummy = 'X';

D
-
X

Check the plan:

Hotsos Symposium 2014

After missing last year’s Hotsos Symposium (trying to cut my travel as you know :), I will present at and deliver the full-day Training Day at this year’s Hotsos Symposium! It will be my 10th time to attend (and speak at) this awesome conference. So I guess this means more beer than usual. Or maybe less, as I’m getting old. Let’s make it as usual, then :0)

Oracle X$ tables – Part 1 – Where do they get their data from?

It’s long-time public knowledge that X$ fixed tables in Oracle are just “windows” into Oracle’s memory. So whenever you query an X$ table, the FIXED TABLE rowsource function in your SQL execution plan will just read some memory structure, parse its output and show you the results in tabular form. This is correct, but not the whole truth.

Check this example. Let’s query the X$KSUSE table, which is used by V$SESSION:

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