Re: What is Parallel DML?

You don't mention it, but I hope you remembered the side-effects of delayed block cleanout. The change from 40-60 seconds to 'a few seconds' seems a bit extreme for simply doubling up to 2 PQ slaves - I wouldn't have expected anything better than a 2x improvement.

Another factor which could help to explain the difference, though:
The serial scan may have found numerous blocks in the buffer already, and therefore had to skip them on the serial scan, hence producing much smaller multiblock reads. On the other hand PQ scans are direct and 'always' do a full MRBC on their scans.

On the down side, PQ scans flush dirty blocks to disk before starting to read - which could produce differences in performance between test cases and production systems (and would tend to favour PQ tests run immediately after restarting Oracle).

--
Jonathan Lewis

Host to The Co-operative Oracle Users' FAQ
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Billy Verreynne wrote in message <9johq6$g0n$1_at_ctb-nnrp1.saix.net>...


>

>I loaded the Oracle 7.1 table with a bunch of detailed claim rows for a

 specific


>medical aid plan, for a specific month. I choose the smallest of the

 plans -


>where about 35,000 claims are received per month. The easiest way to test

 PQ is


>a simply SELECT COUNT(*). This uses a full table scan. The SELECT COUNT(*)

>without PQ took as I recall, about 40 to 60 seconds to complete. Shutdown

 and


>reboot the machine. Then I ran the SELECT COUNT(*) with 2 PQ's. The

 response was


>within a few seconds. After that I experimented with more PQ's - running

 NT's


>Performance Manager to monitor perfomance. Conclusion : 2 PQ's on that

 specific


>single CPU platform (a friggen 200mhz Pentium!) provided the best

 performance


>when doing this table scan. Now tell me again that PQ does not work on a

 single


>CPU platform.

>

>

>Anyway, this pointless bickering is making me thirsty. You buying or

 what..?


>

>--

>Billy

>