on 9i (on unix AIX how can we verify if there were some locks in DB in last 5 hours ?
Oracle doesn't keep a historical record of locks.
What is the actual problem you're trying to solve with this information?
I think you can use a Statspack report, but it doesn't give information particular locks. AWR came with 10G.
For issues related to Deadlocks,refer to :
Document 60.1 Troubleshooting Assistant: Oracle Database ORA-00060 Errors on Single Instance (Non-RAC) Diagnosing Using Deadlock Graphs in ORA-00060 Trace FilesDocument 1509919.1 Master Note for Database Error ORA-00060