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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