PDQ Question and clarification

Probably a gimme question for gurus: Am I correct in the following assumptions: The sql stmt Set PDQPRIORITY HIGH/LOW/0 is specific to that block of sql statements and is overridden by the IDS instance config params and overrides the generic user env variable. PDQPRIORITY=HIGH/LOW/0 as a user env variable is session specific and is controlled by the overall config paramaters by the instance. Config parameters MAX_PDQ, DS_xxx are generic to the instance and control and override session specific env variables. To use PDQ you need to set the Informix onconfig params AND environ variables or sql statements. PDQ is best used with a good fragmentation strategy. Other points of advice as I implement it? The app is primarily a OLTP but does get some heavy DSS hits.

dios wrote: > > Probably a gimme question for gurus: > > Am I correct in the following assumptions: > > The sql stmt Set PDQPRIORITY HIGH/LOW/0 is specific to that block of sql > statements and is overridden by the IDS instance config params and overrides > the generic user env variable. The SET PDQPRIORITY is the same as the environment variable below. It takes affect when run and lasts until the end of the session or until changed. It is limited by the ONCONFIG MAXPDQPRIORITY parameter, the % that is specified is a % of MAXPDQPRIORITY. HIGH = 100, MED = 50%. > PDQPRIORITY=HIGH/LOW/0 as a user env variable is session specific and is > controlled by the overall config paramaters by the instance. Same as above, except that the value in effect in the environment when the engine was started acts as a default. > Config parameters MAX_PDQ, DS_xxx are generic to the instance and control > and override session specific env variables. Control and limit not override. There is no longer an ONCONFIG parameter PDQPRIORITY as a default although the PDQPRIORITY env ver set when the engine started serves as a default. > To use PDQ you need to set the Informix onconfig params AND environ > variables or sql statements. Yes, more or less. > PDQ is best used with a good fragmentation strategy. Yes but effective even without fragmentation. > Other points of advice as I implement it? The app is primarily a OLTP but > does get some heavy DSS hits. Then set PDQ for the DSS sessions or in the source then cancel it before any OLTP queries as it will hurt them. Art S. Kagel