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Oracle Invalidations

Oracle Consulting Tips by Burleson

 

The Invalidations Oracle metric is the number of times objects were invalidated. For example, an object is invalidated automatically by Oracle when it is no longer safe to execute. For example, if the optimizer statistics for a table were recomputed, then all SQL statements currently in the library cache at the time the recompute occurred would be invalidated, because their execution plans may no longer be optimal.

You can see invalidations with this script:

select b.namespace "Name Space"

     , e.gets - b.gets  "Get Requests"

     , to_number(decode(e.gets,b.gets,null,

       100 - (e.gethits - b.gethits) * 100/(e.gets - b.gets))) "Get Pct Miss"

     , e.pins - b.pins "Pin Requests"

     , to_number(decode(e.pins,b.pins,null,

       100 - (e.pinhits - b.pinhits) * 100/(e.pins - b.pins))) "Pin Pct Miss"

     , e.reloads - b.reloads                                   "Reloads"

     , e.invalidations - b.invalidations                       "Invalidations"

  from dba_hist_librarycache  b

     , dba_hist_librarycache  e

 where b.snap_id         = &pBgnSnap

   and e.snap_id         = &pEndSnap

   and b.dbid            = &pDbId

   and e.dbid            = &pDbId

   and b.dbid            = e.dbid

   and b.instance_number = &pInstNum

 

SEE CODE DEPOT FOR FULL SCRIPTS

 

The following is a possible result of this query.

 

SQL> @ Lib_cache_int_10g.sql

 

Name Space      Get Requests Get Pct Miss Pin Requests Pin Pct Miss    Reloads Invalidations

--------------- ------------ ------------ ------------ ------------ ---------- ------

BODY                    1840   5,76086957         3117   4,39525184         24      0

CLUSTER                  216   2,31481481          532   1,12781955          1      0

INDEX                     37   97,2972973           41    87,804878          0      0

JAVA DATA                  3   33,3333333            5           40          0      0

JAVA RESOURCE              0                         0                       0      0

JAVA SOURCE                0                         0                       0      0

OBJECT                     0                         0                       0      0

PIPE                       0                         0                       0      0

SQL AREA               31706     7,459156       120148   2,84482472        495     60

TABLE/PROCEDURE        13926   17,6576188        83460    5,5415768        425      0

TRIGGER                  119   14,2857143          488   3,89344262          2      0

 

Oracle MOSC Documents also discuss the invalidation meter in respect to Java applications, "The updates and invalidations to the objects in the component cache are distributed across other JVMs. This means that the keys that you are putting into the cache must be serializable."

    
This, and many other Oracle performance metrics are discussed in my book "Oracle Tuning" by Rampant TechPress.  You can buy it directly from the publisher and save 30% at this link:

http://www.rampant-books.com/book_1002_oracle_tuning_definitive_reference_2nd_ed.htm


 

 

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