Re: Performance question

Willie L. Meeks wrote: > > I have a question related to PDQ. Can any one explain to me why when you > run a query with PDQ enabled it appears that your cpu vp's don't work as > hard. It appears to me from the results I have observed from my DSS system > that if I excute 50 without PDQ enabled the box works hard and the queries > complete faster. > > When PDQ is enabled the cpu vp's only are working at about 45 to 50 > percent of capacity as well as sar reports indicate that this is consistent > with informix. Can some please give me some advice on possible performance > gains. If you set PDQ% very high each query will wait until it can get at least that percent of the total resources (memory & CPU) if PDQPRIORITY=55 for all 50 queries then the queries single thread and the currently running query only uses 55% of the CPU and memory configured. This is to leave resources for non-DSS queries and insure that DSS queries do not run when resources are tight. To get 50 processes to run efficently and use most available resources set PDQPRIORITY such that >90% of resources will be used by the currently running mix (ie PDQPRIORITY=15 will let 6 queries run simultaneously using 90% of available resources). remember the PDQPRIORITY 1 and 2 are special values. Art S. Kagel