Parse CPU to Parse Elapsed

Parse CPU = amount of CPU time used for parsing.
Parse Elapsed = amount of clock time used for parsing.

Parse Elapsed = Parse CPU + Wait time.

Parse CPU to Parse Elapsed ratio = 100 * parse CPU/ parse Elapsed.

Ideally Parse Elapsed must be equal to Parse CPU, i.e., only CPU time is used for parsing. In that case the ratio is 100%. If wait time is more then the ratio will be less.

Low Value for this ratio is an indicator of latching problem. Investigate the latch sections in AWR and Statspack report for contention on library cache and shared pool latches.