On Apr 16, 2004, at 4:23 AM, Rajesh Kumar Mallah wrote:

I am running an update on the same table

update rfis set inquiry_status='APPROVED' where inquiry_status='a';

 Its running for past 20 mins. and top output is below.
 The PID which is executing the query above is 6712. Can anyone
 tell me why it is in an uninterruptable sleep and does it relate
 to the apparent poor performance? Is it problem with the disk
 hardware. I know at nite this query will run reasonably fast.

I've had this problem recently. The problem is simply that the disk cannot keep up. Most likely you don't see it at night because traffic is lower. There are only 2 solutions: 1. get more disks 2. write to the db less

The machine I was running on had a single(!) disk. It was a quad xeon so there was plenty of cpu. I'd see 8-9 processes stuck in the "D" state. Doing a simple ls -l somefile would take 10-15 seconds and of course, db performance was abysmal.

I had a lowly P2 with a few disks in it that was able to run circles around it for the simple fact the machine was not waiting for disk. Again, proof that disk is far more important than CPU in a db.

good luck.


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