FAQ
We have an open service request with SAP where we are working on an Oracle performance issue related to Oracle 11.2.0.1 and securefiles.
SAP is asking us to run the calibrate_io process. Does this have any purpose internal to the database other than showing information about io stats? Does it affect the optimizer based on io response?

I have found lots of links that explain how to run the calibrate_io process for Resource Manager and how to look at the results - but none that seem to take the next step to explain why you are doing this or whether or not the optimizer will take this information into consideration when doing an explain plan.

Does anyone have experience with this process? Is it just simply a tool to measure io performance like Orion and no other purpose in life - so to speak?

Thanks!
Bill Johnson

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  • Goulet, Richard at Nov 21, 2011 at 1:39 pm
    Bill,

    The 11g Optimizer is supposed to take system statistics into account.

    Richard Goulet
    Senior Oracle DBA/Na Team Leader


    -----Original Message-----
    From: oracle-l-bounce@freelists.org On Behalf Of Johnson, William L (TEIS)
    Sent: Monday, November 21, 2011 8:20 AM
    To: ORACLE-L
    Subject: What is the purpose of DBMS_RESOURCE_MANAGER.CALIBRATE_IO?

    We have an open service request with SAP where we are working on an Oracle performance issue related to Oracle 11.2.0.1 and securefiles.
    SAP is asking us to run the calibrate_io process. Does this have any purpose internal to the database other than showing information about io stats? Does it affect the optimizer based on io response?

    I have found lots of links that explain how to run the calibrate_io process for Resource Manager and how to look at the results - but none that seem to take the next step to explain why you are doing this or whether or not the optimizer will take this information into consideration when doing an explain plan.

    Does anyone have experience with this process? Is it just simply a tool to measure io performance like Orion and no other purpose in life - so to speak?

    Thanks!
    Bill Johnson

    --
    http://www.freelists.org/webpage/oracle-l


    --
    http://www.freelists.org/webpage/oracle-l
  • Dom Brooks at Nov 21, 2011 at 2:03 pm
    Calibrate_io also affects auto dop operations.

    Cheers,
    Dominic
  • Grzegorz Goryszewski at Nov 21, 2011 at 3:54 pm

    On 2011-11-21 14:20, Johnson, William L (TEIS) wrote:
    We have an open service request with SAP where we are working on an Oracle performance issue related to Oracle 11.2.0.1 and securefiles.
    SAP is asking us to run the calibrate_io process. Does this have any purpose internal to the database other than showing information about io stats? Does it affect the optimizer based on io response?
    Hi,
    please check:
    *Automatic Degree of Parallelism in 11.2.0.2 [ID 1269321.1]
    ...*

    When |PARALLEL_DEGREE_POLICY| is set to |AUTO|, Oracle Database
    determines whether a statement should run in parallel based on the cost
    of the operations in the execution plan and the hardware characteristics.

    The hardware characteristics include I/O calibration statistics so these
    statistics must be gathered otherwise Oracle Database does not use the
    automatic degree parallelism feature.


    *
    and be aware of:
    **Bug 10180307 - Dbrm dbms_resouce_manager.calibrate_io reports very
    high values for max_pmbps [ID 10180307.8]

    Regards
    GregG

    *

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