Hi Arun,
Please compare the RUN for job ran on the affected day and other day.
You can do this by
SM37--> select the job --> Goto Job statistics.
In following screen you can check the
Most of the time spent on
Number of records processed
Path of execution
If listed you can also find the tables included in the run...
This will help you to drill down your problem.
Regards,
Prithviraj.