Oracle OEM show a chart of disk performance, as shown in the chart below. when the OEM target database is 10gr2, the number of average disk response time (ms) is 0.01 ms, which unreasonable low. when the target database is 11gr2, the number is about 10ms, which I think is reasonable. it's time to find out where the discrepency comes from.        The backend query is this one:   set linesize 200  col name format a9  col path format a19  --col MB_per_sec format  select t3.name,t2.name,t2.path,t2.reads,t2.read_time,round(t2.read_time/t2.reads*1000,3) rd_rspd_ms,t2.writes,round(t2.write_time/t2.writes*1000,3) wr_rspd_ms,  round((t2.read_time+t2.write_time)/(t2.reads+t2.writes)*1000,3) dsk_rspd_ms,round((t2.bytes_read+t2.bytes_written)/1024/1024/(t2.read_time+t2.write_time))  MB_per_sec from V$asm_disk t2, v$asm_diskgroup t3  where t3.group_number=t2.group_number  order by 1,2  /    NAME      NAME      PATH               ...
 
 
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