Oracle Database Discussions

Hello All-

I am working on a script to find out the wait events contribution based on DB Time, but for a specific interval, wait time is more than DB event ?????

I take 2 samples, say between 5 seconds

Sample A :

DB Time : select value from v$sys_time_model where stat_name = 'DB time';
Event Time : select event, value from v$system_event where wait_class != 'Idle'

then again, after 5 seconds

Sample B :

DB Time : select value from v$sys_time_model where stat_name = 'DB time';
Event Time : select event ,time_Waited_micro_fg from v$system_event where wait_class != 'Idle'


then I calculate the Delta DB Time and Delta Event waited_micro... but some time event delta is much higher than DB time. is there anything I am missing,
I noticed, during the test load. "db file scattered read" was showing higher delta time than DB delta.

As per oracle documentation, my understanding is DB Time is sum of all non-idle wait times, wasn't able to understand how come a specific event can have more time than DB time.

Any comments will be appreciated.