Re: Using NetApp Filers for a DWH

From: Hemant K Chitale <hkchital_at_singnet.com.sg>
Date: Thu, 05 Aug 2004 23:14:33 +0800
Message-Id: <6.1.2.0.0.20040805231323.025b1b18@pop.singnet.com.sg>

I will be running 9i and Linux against the NetApp. However, I will try collecting performance statistics and trace files.

Thanks

At 07:46 AM Thursday, you wrote:
For your second question: The WAFL technology can have a disastrous effect on full table scans and fast full scans in Oracle10g. You can create this simple mouse trap:-

1. Create a table and load a bunch of data.
2. Flush the buffer cache.
3. Enable 10046 at level 8 for the session.
4. set timing on
5. set db_file_multiblock_read_count = 16
6. perform a full table scan against the table. (this is your baseline)
7. exit
8. login again
9. run a procedure that updates the 1st row of every other block (i.e. odd or even blocks)
10. repeat steps 2 to 6. Note the elapsed times and compare the two trace files.

According to my tests in Oracle10g, many db file sequential read events showed up in the trace file after the update. I have seen as much as 89% degradation in performance. NetApp blamed this on Oracle as a 10g bug. Oracle kinda admitting it, but until now there is no resolution. However, when the same test was ran in Oracle 9.2.0.4 it didn't produce this problem.

-Richmond Shee.

Hemant K Chitale
Oracle 9i Database Administrator Certified Professional http://web.singnet.com.sg/~hkchital

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Received on Thu Aug 05 2004 - 10:09:56 CDT