an useful article http://dbakevlar.blogspot.com/2010/02/lead-developer-and-i-have-been-working.html
I love parallel. I am thrilled with the performance gains I can attain when hashing large tables when accessing multiple partitions. I do not love parallel when someone decides to put a group by or order by into the statement. If any sorting has to occur on the statement, I've been seeing some odd behavior in about 80% of the executions. It appears that when sorting, it's not Oracle sorting the data all at once, but sorting one parallel slave's data set at a time. This creates an escalation in temp space usage that can become insanely difficult for Oracle to process efficiently and performance degrades immensely.
Carefully test any parallel processing when sorting is involved. You may not receive performance benefits as expected.
Filtering LOBs - A two-part question about the FILTER operation appeared on the Oracle-L list server yesterday. The first part was a fairly common question – one that’s oft...
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