Re: need performance help: avoid starvation of short queries by long-running queries

On 3 Oct 98, at 10:10, Dean Thompson wrote: > We are running Informix Online on a 4-processor HP machine. Our application > uses primarily short update transactions and short queries, but some user > requests can generate queries that retrieve thousands of records. Our > problem is that each long-running query appears to (approximately) consume a > processor until it completes. If four long-running queries happen to end up > running simultaneously, then every newly-arriving short query appears to > starve until one of the long-running queries completes and frees up a > processor. > > I would have assumed that preventing long-running queries from starving > short ones would have been a basic Informix design issue, and that Informix > would use a fair enough scheduling algorithm to avoid this. Obviously we > must also consider lock conflicts, but if only three processors are consumed > by long-running queries then short queries still complete. I am inclined to > believe that we are overlooking a configuration or query-design issue. Well, it depends. If you are making use of Parallel Data Query (PDQ) in these long-running queries, then you are contributing to the scheduler's decision to allocate more resources to the long- running queries. Check the setting of the PDQPRIORITY environment variable or if you have a SET PDQPRIORITY x statement in your SQL. Also check the value of MAXPDQPRIORITY. if both of these are > 0, you might want to reduce them and see what happens. PDQ is a bit more than I can dredge out of my memory on a Monday morning, hit the Administrator's Guide and check out PDQ. :-) HTH. -- Ciao, Billy /Group Managing Director, The West Solutions Group: http://www.west.co.za \\ Drivel @ http://www.west.co.za/tasteless/ / \\ "Granted, Mr Wheeler's ideas are stupid and unreasonable, but he does own the company and I / think we should go along with him..." \\________________________________________________________________________________________________