Re: Long-running queries

>In article <3uk28e$ccg@lennon.cc.gatech.edu>, gukal@cc.gatech.edu says... > >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. Since I found this (being replied to) in the Rdb newsgroup, I think it's fair to ask: Have you looked at Rdb to see how it stacks up against the others? If you haven't heard of Rdb, consider that the Oracle corporation has heard of it. So much so, that they decided it was worth a hundred megabucks to own it. Rdb has a few features that make coexistence between OLTP and DSS a little less painful. An example is the snapshot feature. With snaphots enabled, the snapshot reader need not lock any data in order to get a consistent view of the data throughout the (read only) transaction. This reduces contention between readers and writers, at the expense of making the writers pay an overhead cost of writing before images of updated records into a snapshot file. Havin said that, I think most RDB sites that want to go into both OLTP and DSS heavily are finding it advantageous to have a pair of databases, with some fairly significant design differences between them. If the physical features of the database are optimized for LOTP, the effect on DSS is at best neutral, but usually to degrade throughput. Likewise, the decision about how much deliberate denormalization to indulge in is usually different for OLTP and DSS. At my site, we've gone one step further: We use Rdb for the big OLTP application, and copy selected data to an Oracle database for mid term archival, and to support reporting and DSS type of activity. Regards, Dave +-------------------------------------------------------------------+ | Any opinions expressed above are solely my own and do not | | reflect a commitment of any kind by my clients or employers. | +-------------------------------+-----------------------------------+ | David G. Cressey | | | 73230.1665@compuserve.com | This sentence no verb. | | cressey@rzdisk.enet.qntm.com| | +-------------------------------+-----------------------------------+