Re: PDQ Advice Please

Tony Flaherty wrote: > > HI, > > Hp-Ux 10.20 > IDS 7.30.UC7 > > We have a OLTP set-up with occasional large queries/updates running during > the day. I've not paid that much attention to the PDQ settings previously > :o/ I thought it was disabled. However I've started reading up on it in the > hopes that I can use it to reduce the impact of the bigger update programs > that are run. Impact to who? Themselves? :-) It is not wise to try and mix OLTP with DSS type operations. You may end up speeding up your batch type jobs at the expense of your OLTP access. But then they WOULD finish quicker. ;-) > My current ONCONFIG params for PDQ are; > > MAX_PDQPRIORITY 100 # Maximum allowed pdqpriority > DS_MAX_QUERIES # Maximum number of decision support queries > DS_TOTAL_MEMORY # Decision support memory (Kbytes) > DS_MAX_SCANS 1048576 # Maximum number of decision support scans> > NOTE that there is no entry for PDQPRIORITY, TFM indicates that there > should be an entry for this and it should be zero. Is this the default > since there isn't one, is my manual out of date or is my instance configured > incorrectly? Your manual is either out of date or referring to the environment variable PDQPRIORITY. There is no longer a configuration parameter with that name since about version 7.10. Hence PDQ is OFF by default, and must be switched on at the session level with either the aforementioned environment variable or the SET PDQPRIORITY SQL command. > A MAX_PDQPRIORITY of 100 appears to be bad! is it? No. > From my understanding of > TFM I would of thought if PDQ was active on my machine I would be having > real problems with the above settings. No. > If I set PDQPRIORITY to zero in the ONCONFIG and then assign values to the > other PDQ parameters, do they have any effect? PDQPRIORITY does not, the others do, as soon as you switch PDQ on. :-) > Also, am I correct in saying that I can modify my heavy process > (Informix-4GL) so that it issues a SET PDQPRIORITY stmnt to reduce its > impact on the system. If so can you recommend a % to use? or indeed any > other methods of reducing its impact, I was toying with the rather inelegant > idea of placing a SLEEP 1 in an appropriate place :o(. Well it depends on what you mean by impact. If you give it more resources, like PDQ, then it will have a bigger impact on other processes. However, you may deem it good to get it over with as quickly as possible. The percentage is not as important as the amount of resources you throw at PDQ. Certainly you can then reduce those resources using the percentage or distribute them among many PDQ processes. Cheers, -- Mark. +----------------------------------------------------------+-----------+ | Mark D. Stock mailto:mdstock@mydas.freeserve.co.uk |//////// /| | http://www.informix.com http://www.informixhandbook.com |///// / //| | http://www.iiug.org +-----------------------------------+//// / ///| | |What year 2000 bug? year 2000 bug? |/// / ////| | |year 2000 bug? year 2000 bug? year |// / /////| | |2000 bug? year 2000 bug? year 1900 |/ ////////| +----------------------+-----------------------------------+-----------+