master table vs log table in 11.1.0.7 database

Hi,

database version=11.1.0.7

We have one perfomance issue where it is resolved but just want to know the root cause for this?

issue:application team is runnning the job from java application where it will truncate the table who have two partitions.Table count have 5crore rows.

2 months back same job took just 20 minutes but now after triggering the job it is taking more than 4 hours but still runnig.

-->i have eliminated stats is not the problem and there is no change is database level/OS level/application level.

-->i dont have baseline report where the job ran successfully last 2 months back.