RE: Changes to RULE based optimizer between Oracle8 and 9i

Well if optimiser_mode=3Drule with stats doesn't invoke CBO then I =
wonder why OEM is providing me with cost data??

Dick Goulet
Senior Oracle DBA
Oracle Certified 8i DBA

-----Original Message-----
From: Keith Moore [mailto:kmoore7@xxxxxxxxxxxx]
Sent: Friday, January 30, 2004 12:59 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: Changes to RULE based optimizer between Oracle8 and 9i



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We tried both queries with and without statistics. Same results.

Are you sure about OPIMIZER_MODE=3DRULE invoking the CBO if there are =
statistics. The Reference manual says otherwise (not that it's never =
been wrong).
  ----- Original Message -----=20
  From: Goulet, Dick=20
  To: Multiple recipients of list ORACLE-L=20
  Sent: Friday, January 30, 2004 11:39 AM
  Subject: RE: Changes to RULE based optimizer between Oracle8 and 9i


  Logic says one thing, experience says another.  Question one, are the =
tables analyzed?  If so, since RBO is deprecated in 9i even setting =
OPTIMIZER_MODE=3DRULE will invoke the CBO.

  Dick Goulet
  Senior Oracle DBA
  Oracle Certified 8i DBA=20

    -----Original Message-----
    From: Keith Moore [mailto:kmoore7@xxxxxxxxxxxx]
    Sent: Friday, January 30, 2004 11:54 AM
    To: Multiple recipients of list ORACLE-L
    Subject: Changes to RULE based optimizer between Oracle8 and 9i


    We move an application that uses OPTIMIZER_MODE=3DRULE from Oracle8 =
to 9i. Most of it is fine, but there are two queries that have a very =
different execution plan. In one case, the execution time increases from =
less than a minute to more than an hour. Neither query uses any of the =
new Oracle 9i features.

    My understanding is that the Rule optimizer code has not changed, =
except to account for new features like IOT's. Has anyone else seen this =
type of behavior?

    Keith Moore
    Oracle Certified Professional
    972-431-5126
    kmoore7@xxxxxxxxxxxx



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