what is the difference between a child cursor and a parent cursor? > > From: Riyaj Shamsudeen <rshamsud@xxxxxxxxxxxx> > Date: 2004/03/31 Wed PM 12:15:42 EST > To: oracle-l@xxxxxxxxxxxxx > 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 > > > > > > The information transmitted is intended only for the person or entity to > which it is addressed and may contain confidential and/or privileged > material. If the reader of this message is not the intended recipient, > you are hereby notified that your access is unauthorized, and any review, > dissemination, distribution or copying of this message including any > attachments is strictly prohibited. If you are not the intended > recipient, please contact the sender and delete the material from any > computer. > >Title: Message
Let me
try to keep this alive.. Responses in line..
HTH
Thanks
Riyaj "Re-yas" Shamsudeen
Certified Oracle DBA
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