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We have an oracle server with 8 cores and 12gb ram. It's CentOS 5.6 and it has 12gb swap file. Oracle's memory target is 4gb and memory management is automatic. It has MegaSAS Raid controller with 4 drives.

Database itself is around 15gb with lots of blob data.

During sql selects server hangs a lot with high waiting for io, around 100%. It hangs in a way that I can't even connect to it using ssh. It eats around 5-6 gigs of swap. selects doesn't include blob data only plain rows.

I have vm.swappiness = 0 and I even tried swapoff but it still hangs.

What might be the problem?

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Is that a 64-bit CentOS 5.6? –  Janne Pikkarainen Sep 2 '11 at 12:17
@Janne yes it's 64-bit Centos 5.6 with all latest updates installed –  Troydm Sep 2 '11 at 12:19
Did you configure shared memory settings and/or hugepages as Oracle suggests you to do? download.oracle.com/docs/cd/B28359_01/install.111/b32002/… –  Janne Pikkarainen Sep 2 '11 at 12:24
@Janne actually i didn't installed oracle on this server, someone else did it. But i think shared memory is configured correctly –  Troydm Sep 2 '11 at 12:31

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