Interpreting utlestat report

 In reviewing utlestat reports on several of our databases I have noticed several things that raised my eybrows – not with the performance per se (though there is plenty there as well!) but with some things that just don’t look “right.”

1. negative numbers for “logons current”
2. negative numbers for “opened cursors current”
3. negative numbers for “session uga memory”
4. negative numbers for undo segment XACTS
5. counts for blocks_read and block_changes, but no physical reads or writes. I assume this indicates everything was in the buffer pool but am not ready to have my feet held to the fire on it.

Also I’ve been playing around with the SHARED_POOL_SIZE, trying to get some get hit ratios back up above 90%. Perhaps I need more observation periods, but I see at one increase of the SHARED_POOL_SIZE, the get hit ratio for the SQL area improved but the table/procedure are got worse. In studying back through my materials from the tuning workshop, it seems that the only item to impact any of these is the SHARED_POOL_SIZE, which also impacts the data dictionary cache. How does Oracle8 determine how much of the shared pool to give to the different areas of the library cache and the data dictionary cache?

TIA

--
Ed Stevens
(Opinions are not necessarily those of my employer)


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