Connor, Well, technically that answers the "why"... with Oracle's "because I said so" :)
the REAL question is why 3 and not 2 or 4 or 10 or..... ? Rachel --- Connor McDonald <[EMAIL PROTECTED]> wrote: > "RTM" :-) > > Performance Guide 9.2 > > "Caching Session Cursors > > (blah blah blah) > > Oracle checks the library cache to determine whether > more than three parse requests have been issued on a > given statement. > > (more blah blah blah)" > > hth > connor > > > --- [EMAIL PROTECTED] wrote: > I wasn't aware > of it requiring three calls before > > being useful. > > > > Why is that? > > > > Jared > > > > > > > > > > > > "Cary Millsap" <[EMAIL PROTECTED]> > > Sent by: [EMAIL PROTECTED] > > 07/25/2002 07:58 AM > > Please respond to ORACLE-L > > > > > > To: Multiple recipients of list ORACLE-L > > <[EMAIL PROTECTED]> > > cc: > > Subject: RE: Cursor Sharing| Soft > > Parsing > > > > > > Well, three times, right? I think it takes three > > parse calls before > > session_cached_cursors begins to help. But 3 is > > still O(1). Once per > > call is O(#executions). > > > > > > Cary Millsap > > Hotsos Enterprises, Ltd. > > http://www.hotsos.com > > > > Upcoming events: > > - Hotsos Clinic, Jul 23-25 Chicago > > - Miracle Database Forum, Sep 20-22 Middlefart > > Denmark > > - 2003 Hotsos Symposium on OracleR System > > Performance, Feb 9-12 Dallas > > > > > > > > -----Original Message----- > > Still > > Sent: Thursday, July 25, 2002 2:38 AM > > To: Multiple recipients of list ORACLE-L > > > > On Wednesday 24 July 2002 22:08, MacGregor, Ian A. > > wrote: > > > Please define soft parsing. Oracle needs to check > > that the user > > > submitting a SQL statement has permissions to run > > it. It has to do > > this > > > every time a statement is run, bind variables or > > not. > > > > No, code that uses bind variables need only parse > > SQL statements > > once if session_cached_cursors is set. Further > > executions of the same > > SQL don't require a hard or soft parse. > > > > Jared > > > > > When "cursor-sharing" converts a statement to use > > bind variables it > > would > > > save on hard parsing, if a match were found the > > pool; also, it could > > lessen > > > the number of statements present in the pool. > > > > > > Ian MacGregor > > > Stanford Linear Accelerator Center > > > [EMAIL PROTECTED] > > > > > > -----Original Message----- > > > Sent: Wednesday, July 24, 2002 9:23 PM > > > To: Multiple recipients of list ORACLE-L > > > > > > > > > Mike, Kirti, > > > > > > Try page 441 > > > > > > CURSOR_SHARING=FORCE does improve badly written > > applications that use > > lots > > > of literals. > > > However coding should be done using bind variables > > in almost all > > occasions. > > > > > > CURSOR_SHARING=FORCE reduces the hard parsing. > > > > > > What CURSOR_SHARING=FORCE does is rewrites all > > queries to use bind > > > variables before parsing. > > > > > > eg. select ename from emp where empno = 10; > > > rewritten as > > > select ename from emp where empno =:SYS_B_0 > > > or in 8.1.6 , 8.1.7 > > > select name from emp where empno =:"SYS_B_0" > > > > > > So it substitutes the literal with bind variables > > but incurs the cost > > of > > > soft parsing the statement. > > > Soft Parsing too frequently limits the scalability > > of applications and > > > sacrifices optimal performance which could have > > been achieved in the > > first > > > place if written using bind variables. > > > > > > Parse once and execute as many times as we like. > > > > > > Also check out Bjorn's paper on bind variables and > > cursor sharing at > > > > > > http://technet.oracle.com/deploy/performance/pdf/cursor.pdf > > > > > > So CURSOR sharing is not the "silver bullet" as > > one may expect. > > > > > > Regards > > > Suhen > > > > > > On Thu, 25 Jul 2002 10:23, you wrote: > > > > Mike, > > > > What is the version of the database? Some > > versions of 8.1.7 had a > > few > > > > bugs when this parameter was set to FORCE. I > > suggest searching > > Metalink. > > > > But it does work as advertised in later > > releases. I would also > > recommend > > > > reviewing Tom Kytes' book to read about his > > views in using this > > parameter > > > > at the instance level (my boss is reading my > > copy, so I can't give > > you > > > > page #s). > > > > > > > > - Kirti > > > > > > > > -----Original Message----- > > > > Sent: Wednesday, July 24, 2002 6:08 PM > > > > To: Multiple recipients of list ORACLE-L > > > > > > > > > > > > Has anyone set Cursor Sharing to Force ? > > > > I have a new system that we have to support > > > > and there is alot literals filling up the > > > > pool. I have never changed this parameter > > > > from the default as many seemed to think the > > > > jury was still out on it. However, due to > > > > my situation, I figured I would try it out. > > > > If anyone has any experience with this one > > > > I would be curious to know what happened. > > > > > > > > Mike > > > > > > -- > > > Please see the official ORACLE-L FAQ: > > http://www.orafaq.com > > > -- > > > Author: Suhen Pather > > > INET: [EMAIL PROTECTED] > > > > > > Fat City Network Services -- (858) 538-5051 > > FAX: (858) 538-5051 > > > San Diego, California -- Public Internet > > access / Mailing Lists > === message truncated === __________________________________________________ Do You Yahoo!? Yahoo! Health - Feel better, live better http://health.yahoo.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Rachel Carmichael INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
