EVENT 10235:"check memory manager internal structures"



  7.0 - 10.1.X   Check memory manager internal structures. 

  7.0 - 10.1.X "Check memory manager internal structures" 


  NOTE: Events should NEVER be set by customers unless advised to do so by

      Oracle Support Services. Read [NOTE:75713.1] before setting any event. 

Summary Syntax: 


  EVENT="10235 trace name context forever,  level LL" 

  (Always comment exactly when and why this event is being set) 


                syntax to set this event in sessions. This can cause 

                lots of ORA-600 errors against SGA heaps as not all  

                sessions using the SGA heaps will be using the same event 

                level. This applies to ALL levels except level 65536. 



  The event being set at all causes certain heap checks to be performed. 

   ***  WARNING *********************************************************** 

    ***   This event should only EVER be set at the request of Oracle Support. 

    ***   It can impact performance on most types of system. 

    ***   Level 2 and above can impact latch contention. 

    ***   Level 3 and above can have a *SEVERE* impact on performance. 


  The bottom 3 bits of the level cause the following checks to occur: 

     ~~~~~         ~~~~~~~~~~~~ 

     Level         Description 

     ~~~~~         ~~~~~~~~~~~~ 

        1             Fast check on heap free (kghfrh) 

        2             Do 1 AND fill memory with junk on alloc / free 

        3             Do 2 AND ensure the chunk belongs to given heap on free 

        4             Do 3 AND make permanent chunks freeable so they can  

                      also be checked 

                       This level can give rise to increased memory use 

                       and can trigger false ORA-4030 and false ORA-4031 



  Oracle 9205 onwards only: 

    65536             This is introduced by the diagnostic enhancement in 

                      bug 3293155. It is a totally independent bit setting 

                      which has minimal impact on performance (unless ORed  

                      with other levels). When this is set Oracle tries to 

                      keep comments with "permanent" memory allocations 

                      which can be useful for memory leak problems if the 

                      leaked memory appears to be a leak of "perm" memory. 

                      This level can be set/unset dynamically but will only  

                      store comments in "perm" memory allocated when the  

                      event is set. 


  There are additional values which Oracle Support can use. 




  This event may be used to try to catch HEAP corruption problems closer  

  to when they occur.  Typically level 12 is required to get close to the 

  corruption but this can impact performance too much to be useful. 


Example Output / Interpreting Output: 


  The event should cause an ORA-600 and heapdump to be produced if an 

  error is detected.  









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