Oracle Scratchpad

November 25, 2009

Flash Cache

Filed under: Infrastructure — Jonathan Lewis @ 6:50 pm BST Nov 25,2009

You may have heard about “flash cache” for Oracle 11.2 and Exadata – the clever trick where the code can use flash memory [corrected, thanks to Yas, comment #2] for data that’s “fairly popular” but not quite popular enough to be kept in the data cache by the LRU. The code works to keep a copy of the more useful data on the faster medium to avoid re-reading it from disk.

The technology was originally restricted to Exadata2, but as Guy Harrison reports, a recent patch allows it to run on Oracle Enterprise Linux even when you don’t have Exadata.

Update: See Kevin Closson’s blog item (pingback from comment #4 below) for corrections to this post.


  1. >The technology was originally restricted to Exadata2
    Greg Rahn reports: “not to be confused with the Exadata flash cache” and I can’t search for the note because of stupid MOS error “Recursive error in error-page calling for /secure/error.jspx, see the application log for details.”

    Comment by Timur Akhmadeev — November 25, 2009 @ 8:50 pm BST Nov 25,2009 | Reply

  2. Jonathan, a few corrections, Exadata does not use SSD, it uses flash cards, particularly this one, One difference between Exadata and non-Exadata is, Exadata has the flash cards at the storage side on the cells, in non-Exadata you use the cards on the database server.

    Comment by Yas — November 26, 2009 @ 7:01 am BST Nov 26,2009 | Reply

    • Yas,
      Thanks for the correction (posting now updated) – I have a bad habit of reading “flash memory” and thinking “solid state disk”.

      Comment by Jonathan Lewis — November 30, 2009 @ 10:02 am BST Nov 30,2009 | Reply

  3. […] was recently catching up on my reading of Jonathan Lewis’ blog when I read his post about Flash Cache. Jonathan’s post contained a few comments on the matter and then refers to Guy Harrison’s […]

    Pingback by Pardon Me, Where Is That Flash Cache? Part I. « Kevin Closson’s Oracle Blog: Platform, Storage & Clustering Topics Related to Oracle Databases — December 10, 2009 @ 3:11 pm BST Dec 10,2009 | Reply

  4. Flash Cache is now restricted to Exadata, In the near future, do you think that this feature can be used on other OS environment not made by oracle.

    Comment by adenkang — February 27, 2010 @ 1:58 am BST Feb 27,2010 | Reply

  5. adenkang,

    Flash Cache is not restricted to Exadata. Please click on my ping-back above to learn more.

    Comment by kevinclosson — November 29, 2010 @ 7:36 pm BST Nov 29,2010 | Reply

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