This event appears when a PQ slave has nothing to do, but is not allowed to go idle.
One scenario where you can see large values for the event is when (for example) you have a large data set coming out of a parallel ORDER BY. The last layer of PX slaves in the query will receive a ranged set of rows and sort them. The QC will then request ALL the rows from the first PX slave, then the second, then the third and so on. When the first slave has supplied all its rows, it will go into "PX Deq: Execution Msg" waiting for the QC to tell it do die - which happens only after the QC has got all the rows from all the slaves and passed them to the front end. This means that it is a usually an idle event - but it may be a symptom of excessively large queries choosing an inappropriate execution path. Jonathan Lewis http://www.jlcomp.demon.co.uk Author of: Practical Oracle 8i: Building Efficient Databases Next Seminar - Australia - July/August http://www.jlcomp.demon.co.uk/seminar.html Host to The Co-Operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html -----Original Message----- To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> Date: 17 May 2002 01:22 |Hello, | |I am hoping someone can help me with an elusive wait event called 'PX Deq: |Execution Msg'. As you can see from the statspack "Top 5 Wait Events" this |event accounts for almost 75% of the wait time. I have been looking in past |Oracle-L posts, Google, Oracle FAQ, OTN, Metalink, Oracle manuals, etc. I |can find almost nothing about this event. What I did find leads me to |believe may be an idle event and that it is the second event 'PX Deq Credit: |send blkd' that may be the more troublesome one. However I am still |confused about both. Can someone help set me straight or tell me where |there might be some more information about these 2 events? | |Thanks, |Nancy | |Top 5 Wait Events |~~~~~~~~~~~~~~~~~ Wait % |Total |Event Waits Time (cs) Wt |Time |-------------------------------------------- ------------ ----------- - ----- |-- |PX Deq: Execution Msg 42,144 8,639,803 |74.48 |PX Deq Credit: send blkd 15,339 2,878,443 |24.81 |log file parallel write 41,934 30,787 |.27 |db file parallel write 8,776 25,046 |.22 |db file sequential read 24,767 18,255 |.16 | -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Jonathan Lewis 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).
