Hi ,
You haven't stated clearly that every time you run a particular session, one log file is created or there is a single log file and it is updated or overwritten everytime you run that particular session.
a) If the case is second one, you have to go and manually delete the session logs, no other option.
b) If the case is first one, you can change it at session level.
Edit the session.Go to log and error handling tab.See the option SAVE SESSION LOGS BY TIMESTAMP is checked or not.Most probably it is checked.Uncheck it and check other option i.e. SAVE SESSION LOGS FROM LAST -- SESSION RUNS.
Put 0 at the -- place.Then click ok.
It will make the setting like that only a single log file will be there for that particular session and everytime you run the session it will be overw or updated.
I think this will solve your problem.
Please inform incase of any further problem.
Regards,
Ani.