Oracle Scratchpad

July 27, 2014

Parallel Plans

Filed under: Execution plans,Oracle,Parallel Execution — Jonathan Lewis @ 8:39 pm BST Jul 27,2014

This is the directory for a short series I wrote discussing how to interpret parallel execution plans in newer versions of Oracle.

For other aspects of parallel execution the best, and most wide-ranging, source is  Randolf Geist’s blog, which contains so much material that I’ve had to create a catalogue for my own convenience. All the following links point to work by Randof.

Parallel Data Skew

One of the awkward problems you can encounter with parallel execution is data skew – which has the potential to make just one slave in a set do (almost) all the work hence reducing the performance to something close to serial execution times.  Randolf has written a series of articles on Parallel Skew that has been published by AllthingsOracle over the last few months.



Parallel Execution New Features (12c)






  1. […] operation, which means they can report the wrong order. [Update 3/Jan/2015: Here’s a link to a catalogue of articles that Randolf Geist and I have written about parallel execution plans showing (a.o.) the failure of […]

    Pingback by Interesting Plan | Oracle Scratchpad — January 3, 2015 @ 10:25 am GMT Jan 3,2015 | Reply

  2. Hi Jonathan

    I am not sure however I remember vaguely that I had received an email from couple of back stating bunch of video tutorials on “Oracle Parallelism Mechanism” by Jonathan Lewis up for sale.
    At that time, I did not have much money to spend in dollars or pounds. If above is true, could you please let me know how could I buy those stuffs. There won’t be anyone else who could explain how Oracle do things better than you.

    Thanks and regards,
    Vineet Ranjan

    Comment by Vineet Ranjan — June 13, 2016 @ 6:34 am BST Jun 13,2016 | Reply

    • Vineet,

      I don’t recall doing any parallel execution webinars for AllthingsOracle, but one of the ones I did for SpeakTech is about parallel execution:
      I think Randolf Geist did a couple on parallel execution with AllthingOracle, so maybe you’re thinking of those.

      Comment by Jonathan Lewis — June 14, 2016 @ 9:38 am BST Jun 14,2016 | Reply

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