Question regarding db_file_scattered

From: Johnson, George <GJohnson_at_GAM.COM>
Date: Mon, 18 Jul 2005 14:24:25 +0100
Message-ID: <ECD91EB68018C04CA1B6801EE47A910F3A368558@ntas-ldn15.gam.com>

I have a DB on a Solaris box, the system that is almost at 100% utilisation, I'm not overly worried as no one is complaining, yet. I am simply trying to identify where the resources are being consumed, partly curiosity and partly in the hope of preventing a potential future problem.

I have been over the wait stats and found that the system spends it's time, almost exclusively, making users wait on db_file_scattered_read, about 30% of their session time, in fact. However the OS reports hardly any I/O wait time, the system resources are being used up by user CPU. I believe the entire SGA is little too small, I am wondering if the scattered_read waits are a result of the SGA and/or buffer cache being too small or would a buffer cache that is too small, more likely result in buffer_busy_waits or have I got my thinking completely backside-about-face!? All the notes I can find relate db_file_scattered_read to an I/O performance problem, which from what I can tell from the OS, I don't seem to have.

Any pointers in the direction I should start off in next, would be greatly appreciated.

Rgds

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Received on Mon Jul 18 2005 - 08:26:28 CDT

Question regarding db_file_scattered_read