how to track index usage?

Is it possible to track if an index is being used? I suspect that in our read-only DSS there are indexes that are never used. All access to data is through ad hoc queries. How can I find out if an index was used within the last x number of days? We are running Oracle 7.2.3.  

Thanks  

P.S. One way to do this would be to turn the SQL trace on, but I'd like to avoid that due the added overhead and large amount of output it will create if turned on for several days.  

Petr Schmidt
pgschmid_at_bcsc02.gov.bc.ca Received on Thu Oct 17 1996 - 00:00:00 CEST