According to v$lock_type, the HV enqueue is a: "Lock used to broker the high water mark during parallel inserts" At a guess, this means that Oracle is sharing a single extent across multiple PX slaves while loading instead of using one extent per slave. There seem to be two hidden parameters that might have an impact: Name Default value Description _ctas_hwm_brokered_loads = TRUE Enable HWM brokered CTAS_insert_enable_hwm_brokered = TRUE during parallel inserts high water marks are brokered
There is also a hint HWM_BROKERED which may turn it on, but I can't see a hint that looks like the opposite. It's only a problem if the time spent on the HV enqueue is a significant fraction of the total time to load - bearing in mind that the total time is (probably) shared fairly evenly across the PX slaves - so you may want to divide by the number of slaves before comparing. Regards Jonathan Lewis http://jonathanlewis.wordpress.com Author: Cost Based Oracle: Fundamentals http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html
Date: Fri, 9 Feb 2007 22:21:15 -0800 (PST) From: Sai Selvaganesan <ssaisundar@xxxxxxxxxxxxx> Subject: HV enqueue hii am on a 10gr2 (102.0.2) rac environment and i see enq :HV contention a lot when direct inserts happen (either ctas or insert /*+ append ). The data i am loading is into a LMT of 4m and the amount of data is about 20GB.has anyone seen this contention? if so what does this mean and where am i really hitting a bottleneck.please let me know thx sai
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