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 > -------------------------------------------------------------------- > 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). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Jared Still 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). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Cary Millsap 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).
