Fw: shared pool latch

From: "Sultan Syed" <ssyed@xxxxxxx>
To: "oracle freelists.org" <oracle-l@xxxxxxxxxxxxx>
Date: Thu, 1 Apr 2004 08:39:01 +0400
Message
Thanks Riyaz,I got it.
Syed

----- Original Message ----- 
From: Riyaj Shamsudeen 
To: oracle-l@xxxxxxxxxxxxx 
Sent: Wednesday, March 31, 2004 9:15 PM
Subject: RE: shared pool latch


Let me try to keep this alive.. Responses in line..
HTH
Thanks
Riyaj "Re-yas" Shamsudeen
Certified Oracle DBA
  -----Original Message-----
  From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On 
Behalf Of Sultan Syed
  Sent: Wednesday, March 31, 2004 4:21 AM
  To: oracle freelists.org
  Subject: shared pool latch


  Hi guys
  The following questions are confusing me,please could someone give 
explanation 
  on the below

  1)Is librarycache latch held during the whole process of parse,execute and 
fetch phases ,
  or it is held upto the time searching for the object in hash table and 
release. 

  Library cache latch is held while searching for a parent cursor and 
subsequent child cursor with similar attributes with parent cursor pinned. Also 
library cache latch is held when creating a new library cache object if the 
child cursor is not_found or found_but_not_shareable. Since, parent cursor is 
pinned while searching for a child cursor, I am not sure whether the search for 
child cursor needs to hold on to the library cache latch or not. But if a new 
parent cursor is to be created then the library cache latch must be held.

  Execute and Fetch uses library cache pin and library cache locks to maintain 
the objects from undergoing concurrent modification.

  2)session_cached_cursor caches the child cursor or parent cursors also. 
  As far as I know, session_cached_cursor is searched for pinned child cursor. 
I don't know whether the parent is also kept in the session cached cursor or 
not. 

  3)While doing hard parse which latch is acquired ,shared pool or library 
cache latch or both,
  if it is both which latch will be acquired first? 

  library cache latch is already held while requesting for shared pool latch. 
Shared pool latch is acquired to request/release space from the shared pool 
free memory area and released immediately after that. Request for library cache 
latch can never be made while holding the shared pool latch (at least up to 9i) 
as latch level semantics will prevent that ( as shared pool latch gets are 
always in willing-to-wait mode).

  Thanks in advance
  Syed





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Fw: shared pool latch

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