MVR, The issue we all forget is this: The "Wait Interface" records the last _instrumented_ *wait* event. The process has then moved on to executing in the CPU. However, since there is not "Waiting for CPU" event (and this is not necessarily a "wait" event!!), what you need to do is to look at the "SESSION_STATE" column, and you _will_ see "ON CPU" for this event. What it means is that you most probably had the execution of a multi-level nested loop and all the blocks required was fully in memory, and the last I/O performed was for the index block you mentioned. You should be able to determine the SQL from AWR using the SQLID for that event. The execution plan has changed after the upgrade - so do you have the old plan? John Kanagaraj <>< DB Soft Inc Phone: 408-970-7002 (W) ** The opinions and facts contained in this message are entirely mine and do not reflect those of my employer or customers **