Hi Yechiel, Any full-table-scan in Oracle 8i (or below) consumes 4 LIOs to the segment header. This number has reduced to 2 in 9i. Given that the 1 row that you are going after is in 1 data block, there is 1 LIO for the data block itself, given you a total of 5 LIOs. You can verify this by setting 10046 for the session and looking at the trace output.
The workaround is to reference x$dual in your application. Alternatively, you can create a view on x$dual, create a synonym for it and then go from there. You will incur some I/O for the first access of the query (with the synonym), but subsequent accesses will incur 0 LIOs against x$dual. Cheers, Gaja --- Yechiel Adar <[EMAIL PROTECTED]> wrote: > I did two statspack snapshots, one hour and forty > minutes apart. > Then I generated a report and loaded it into > oraperf.com. > In the report I saw that the two SQL statements that > where executed the most > times where: > > Select xxxx.currval from dual; > > Select xxxx.nextval from dual;. > > Each one was executed about 90,000 times with 5 > buffer gets per execution. > The net result was about 950,000 buffer get for > nextval and currval. > > My question is: > Why should there be about 5 buffer gets per > execution? > > Yechiel Adar > Mehish > -- > Please see the official ORACLE-L FAQ: > http://www.orafaq.com > -- > Author: Yechiel Adar > 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). ===== Gaja Krishna Vaidyanatha Director, Storage Management Products, Quest Software, Inc. Co-author - Oracle Performance Tuning 101 http://www.osborne.com/database_erp/0072131454/0072131454.shtml __________________________________________________ Do You Yahoo!? Yahoo! Games - play chess, backgammon, pool and more http://games.yahoo.com/ -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Gaja Krishna Vaidyanatha 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).
