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Thread: Set isolation for dirty read on Session

  1. #1
    Join Date
    Nov 2000
    Posts
    89
    DBAs:

    Is there a way to set isolation level to dirty read on the "session".


    -Thanks,

    Roger

  2. #2
    As I know, there isn't such a concept as "isolation level" in Oracle. I was very surprised in the begining, but then, looking at the architecture of Oracle and how it works, I did understand why. In fact, in Oracle there are lots of other concepts missing, especially in the locking zone, because of the way it works. For instance, "lock escallation".
    But I think you can do something for modifing the locking behaviour at session level. I don't know very well, but it could be related to "undo retention"...
    The best thing is to wait a response from somebody more experimented, like marist, for instance.

    Marist, please, will you help us, I'm interested too...
    THNX in advance!
    ovidius over!

  3. #3
    Join Date
    Feb 2001
    Posts
    389
    ALTER SESSION SET ISOLATION_LEVEL SERIALIZABLE;

    ALTER SESSION SET ISOLATION_LEVEL READ COMMITTED;

    ALTER SESSION SET ISOLATION_LEVEL READ ONLY;

    Dirty read not allowed.

  4. #4
    Join Date
    Mar 2002
    Posts
    8

    Exclamation :( lock escallation

    ovidius, if no "lock escallation", what happens if one user aquires thousands of row level locks?
    how to manage this situation?

    [Edited by mdan on 03-27-2002 at 10:04 AM]

  5. #5
    Yes, what happens?
    Nothing happens, they aquire it and show must go on...
    Somebody tell Mdan, what happens???
    ovidius over!

  6. #6
    Join Date
    Apr 2001
    Posts
    118
    Buy Tom Kyte's book. Read Chapter 3 on Locking and Concurrency. He explains exactly how Oracle handles such things and why Oracle thinks that "Lock Escalation" is bad for concurrency and why Oracle never does it. He explains it in much better detail than I ever could.

    HTH,

    Heath

  7. #7
    Join Date
    Jun 2000
    Location
    Madrid, Spain
    Posts
    7,447
    Originally posted by Heath
    Buy Tom Kyte's book. Read Chapter 3 on Locking and Concurrency. He explains exactly how Oracle handles such things and why Oracle thinks that "Lock Escalation" is bad for concurrency and why Oracle never does it. He explains it in much better detail than I ever could.

    HTH,

    Heath
    agreed, if you are serious into oracle you should get the book! and chapter 3 is excellent, explains why oracle do that whereas informix or sybase dont etc etc

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