I’ve spent the last week performance tuning for a customer here in Georgia. The biggest thing I found was that they were having a lot of wait issues. To illustrate these wait issues in a simplified method, I used the V$SYSMETRIC view. The query below gives you a comparison between waits and cpu times with ratios.
select metric_name, round(value,2) from v$sysmetric
where metric_name in ('Database CPU Time Ratio', 'Database Wait Time Ratio')
and intsize_csec = (select max(INTSIZE_CSEC) FROM V$SYSMETRIC);