Hi Regarding logging to arcsight . how do i extend the storage of asm logs for more than 1 day.

Clearly the problem is in your ArcSight and not in F5. If you are seeing logs in ArcSight the log data has already left the F5 and is stored on ArcSight. If you can't see more than one day's worth of logs in ArcSight you either have a data retention period set to 1 day in ArcSight (which is really bad) or using a filter in ArcSight to show you only the last 24 hours of logs (which is more likely).