tag:blogger.com,1999:blog-8884584404576003487.post3674073084498488294..comments2024-02-29T09:43:12.251-05:00Comments on ORACLENERD: PARALLEL Rant?oraclenerdhttp://www.blogger.com/profile/12412013306950057961noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-8884584404576003487.post-18401046705242441772010-02-15T16:15:55.290-05:002010-02-15T16:15:55.290-05:00Parallel processing is probably one of the most mi...Parallel processing is probably one of the most mis-understood & abused features of Oracle.<br /><br />I'm pretty sure the great one (a.k.a. tommy boy) said:<br /><br />Parallel != fast<br /><br />Oracle is an incredible system for multiuser (thread/process) processing. It does an incredible job of managing this. Parallel processing, left in the hands of the naive, says give me this huge multicore system and make it my PC for the next few moments. Abused, this can crush the system. <br /><br />Suggest the following:<br />a. do whatever you can to not allow users to run parallel queries. They can wait for their one little thread to complete.<br /><br />b. try using materialized views and query re-write to provide the reporting performance your users desire. <br /><br />c. Question your use of partitioning. Strongly.John Thttps://www.blogger.com/profile/13055594192433564698noreply@blogger.comtag:blogger.com,1999:blog-8884584404576003487.post-15267739133199410772010-02-15T16:06:00.862-05:002010-02-15T16:06:00.862-05:00This comment has been removed by the author.John Thttps://www.blogger.com/profile/13055594192433564698noreply@blogger.comtag:blogger.com,1999:blog-8884584404576003487.post-78165589673663812162010-02-15T13:11:36.401-05:002010-02-15T13:11:36.401-05:00Also, with OBIEE, the end users don't write th...Also, with OBIEE, the end users don't write the queries, BI does. <br /><br />You may need to tell BI in the Logical Layer the layout, what the facts are, dimension tables etc, so that it writes better physical SQL. That can be difficult sometimes with these automated tools, but perhaps having users join in the correct manner and then understanding Physical DB concepts like constraints and indexing (even different kinds of indexing) and the pros and cons with each approach would make them somewhat better IMO.Tomhttps://www.blogger.com/profile/09600876443323337792noreply@blogger.comtag:blogger.com,1999:blog-8884584404576003487.post-17140072235672197722010-02-15T13:08:42.205-05:002010-02-15T13:08:42.205-05:00Parallel does not scale.
Wha?
I heard Tom Kyte d...Parallel does not scale.<br /><br />Wha?<br /><br />I heard Tom Kyte describe this and once I listened, it all made sense. You pretty much described it.<br /><br />If you are "controlled" and you want to make better use of your resources, then in batch situations it makes much more sense than in end user uncontrolled area where people expect their reports to run the same whether they are the only ones running reports or 100 users are running reports.<br /><br />Also to take advantage of resource controls, you need to differentiate between those classes of users so if you use a specific user(s) account for the connections then no problem.<br /><br />HINT, in OBIEE for the Physical table, there is a hint field. You can put parallel hints in there, but I believe you will need to reference the table name completed or use a variable to plug the alias OBIEE gives it automatically, which I am not sure how to do just yet. Would need to dig into the docs/metalink/blogosphere to find out.Tomhttps://www.blogger.com/profile/09600876443323337792noreply@blogger.comtag:blogger.com,1999:blog-8884584404576003487.post-10579631697120154332010-02-15T06:18:38.388-05:002010-02-15T06:18:38.388-05:00Resource Manager can control the degree of paralle...Resource Manager can control the degree of parallel for groups of users - see http://www.oracle.com/technology/products/bi/db/11g/pdf/twp_dw_best_practies_11g11_2008_09.pdf<br /><br />I hate parallel_adaptive_multi_user for user queries - users like to expect that a certain query takes x seconds (whatever the x is!) when it might vary between 0.01*x and 1000X depending on who gets the resource first then that is the recipe for broken reporting SLAs and angry usersPete Scotthttps://www.blogger.com/profile/17524162121927585565noreply@blogger.comtag:blogger.com,1999:blog-8884584404576003487.post-90631719678280444962010-02-15T04:44:45.651-05:002010-02-15T04:44:45.651-05:00I know it's not the real focus of your article...I know it's not the real focus of your article but you've always got parallel_adaptive_multi_user for an element of "control".DomBrookshttps://www.blogger.com/profile/02598622186013843759noreply@blogger.com