Advanced Oracle Troubleshooting Guide – Part 12: control file parallel reads causing enq: SQ – contention waits?

Vishal Desai systematically troubleshooted an interesting case where the initial symptoms of the problem showed a spike of enq: SQ – contention waits, but he dug deeper – and found the root cause to be quite different. He followed the blockers of waiting sessions manually to reach the root cause – and also used my @ash/ash_wait_chains.sql and @ash/event_hist.sql scripts to extract the same information more conveniently (note that he had modified the scripts to (more...)

Sqlplus is my second home, part 8: Embedding multiple sqlplus arguments into one variable

I’ve updated some of my ASH scripts to use these 4 arguments in a standard way:

  1. What ASH columns to display (and aggregate by)
  2. Which ASH rows to use for the report (filter)
  3. Time range start
  4. Time range end

So this means whenever I run ashtop (or dashtop) for example, I need to type in all 4 parameters. The example below would show top SQL_IDs only for user SOE sessions from last hour of ASH (more...)

Oracle Exadata Performance: Latest Improvements and Less Known Features

Here are the slides of a presentation I did at the IOUG Virtual Exadata conference in February. I’m explaining the basics of some new Oracle 12c things related to Exadata, plus current latest cellsrv improvements like Columnar Flash Cache and IO skipping for Min/Max retrieval using Storage Indexes:

Note that Christian Antognini and Roger MacNicol have written separate articles about some new features:



Public Appearances 2015

Here’s where I’ll hang out in the following months:

11-12 Feb 2015: IOUG Exadata SIG Virtual Conference (free online event)

  • Presentation: Exadata Performance: Latest Improvements and Less Known Features
  • It’s a free online event, so sign up here

18-19 Feb 2015: RMOUG Training Days (in Denver)

  • I won’t speak there this year, but plan to hang out on Wednesday evening and drink beer
  • More info here

1-5 March 2015: Hotsos Symposium 2015

Oracle In-Memory Column Store Internals – Part 1 – Which SIMD extensions are getting used?

This is the first entry in a series of random articles about some useful internals-to-know of the awesome Oracle Database In-Memory column store. I intend to write about Oracle’s IM stuff that’s not already covered somewhere else and also about some general CPU topics (that are well covered elsewhere, but not always so well known in the Oracle DBA/developer world).

Before going into further details, you might want to review the Part 0 of this series and also our (more...)

My presentations at OOW 2014 (See you there!)

Here’s where I will hang out (and in some cases speak) during the OOW:

Sunday, Sep 28 3:30pm – Moscone South – 310

Monday, Sep 29 8:30am – 4:00pm (more...)

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 (more...)

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!

We can’t talk much about the technical details before Oracle is officially out in July, but here’s the recorded interview that got published at Oracle website as part of the In-Memory launch today:

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.

So, you can use storage indexes to skip I/Os against your large fact table, based on a (more...)

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.

This is also why Accenture approached us some time ago – and you may already have seen today’s announcement that Enkitec got bought!