We are doing a performance testing on a customer's site and choose RAT (Real application Testing) as the solution to simulate real world workload.
The production system is 10205 and testing system is 11202 on Quarter Exadata X2-2.
During peak business time we capture for 3 hours and get 45G workload file using dbms_workload_capture on prod environment and transfer them to Exadata.
After pre-process and calibrate the client, we start 6 wrc clients to simulate the workload. but after we issued the dbms_workload_replay.start_replay(), the command doesn't return and wrc client also wait at the "wait for replay to start...."
we wait for about a hour, from dba_workload_replays we can see the status shows as "PREPARE" and no any progress so we issued Ctrl + C on the SQLPLUS and dbms_workload_replay.start_replay return immediate. at this time from the wrc client, we can see that "workload start to play...." and from db alert log, we also observed that message indicated that workload start to replay....
Question1: Why dbms_workload_replay.start_replay() doesn't return and why prepare cause so long time, what is it doing? is it because of the capture file too big (45G here)? we do try with a small capture file and there is no this problem..
Question2: Is it suggested to start the wrc client on testing system itself (Exadata compute node here)? Any overhead data for reference here? As we know there are about 4.5% overhead (performance impact) during capture from Oracle guide.
Question3: After Ctrl + C, the replay can be finished, but it takes much longer than we captured. We capture about 3.5 hours but it takes over 8 hours to replay. Is this because we use the sync mode to replay? If not how to control to replay as the same duration as captured.