iASH tool is used for performance analysis of an Oracle system.
iASH gives details of a database state in graphical form. It also helps drill deep into an issue by just point and click approach.
iASH does not need any installations on the database. For performance analysis the user must connect as DBA or user with access to views: gv$active_session_history, gv$sysmetric_history, gv$services and dba_users