gc buffer busy from the same instance??

10.2.0.4 EE on SLES 10

We have seen fairly significant waits recently on this during a large load recently. We know which query is causing it and are submitting a fix, but my question is the following:

When I select from gv$session, I see session x on instance 2 waiting on "db file sequential read" for a given file and block number. I see session y, also on instance 2, waiting on "gc buffer busy" for the same file and block. These are the only two sessions going after this block.

I can understand (and would expect) this if session y was on instance 3, or whatever. However, since both sessions are on the same instance, why is this not either recorded as "read by other session" or "buffer busy waits" event?

Thanks,

Steve Received on Fri May 08 2009 - 14:10:54 CDT