Re: Long-running queries

gukal@cc.gatech.edu (Sreenivas Gukal) wrote: >Hi Folks >Part of my Ph.D. thesis deals with efficiently supporting long-running >queries (maybe Decision Support System queries) without affecting >concurrent transactions in an OLTP environment. I dont know how important >and/or frequent a problem this is in real applications. If you >have encountered similar situations, can you please let me >know the context you had the problem in and what your solution was. The only really good way I have found so far to solve your problem is to have a replicate database against which the long ad hoc queries are run. All solutions where such queries are run against a database where OLTP work is going on, result in performance problems and other kinds of trouble. My experience from practical work is that as soon as ad hoc users are allowed to access a database, there are always users who fire extremly complicated queries (most often it's done unintentionally) that ruin performance for the OLTP:s. To have a separate copy of the database for ad hoc use works fine. There are tools available to ship all updates from the original database to the copy at the desired point in time (immediately, once a day, once an hour or at any other interval). Name: Magnus Weiman Company: Datalogikonsult AB http://DECUS.SE/~weimanm mailto:WEIMANM@DECUS.SE S-mail: Box 52, S-590 79 VRETA KLOSTER, SWEDEN Phone: +46 13 131330 Fax: +46 13 61142 GSM: +46 70 7440806 minicall text: 393662