If Oracle Apps client is idle for some time (Eg. Application user goes for a coffee break) session during that time is called as Idle Session & because of security reason, performance issues and to free up system resource Oracle Applications terminates client session (both forms & self service) after idle time value is reached to the one mentioned in configuration file.
To enter into application, profile option "ICX Session Timeout" is used.
ICX Session Time out mentioned in profile option ICX: Session Timeout is in minutes, so ICX session timeout=30
From where ICX: Session Timeout & session.timeout get values?
Autoconfig determines value for profile option "ICX: Session Timeout" and "session.timeout" from entry in context file ($APPL_TOP/admin/SID_hostname.xml) with parameter s_sesstimeout where value mentioned is in milliseconds so profile option ICX: Session Timeout value should be s_sesstimeout/ (1000 * 60) which means here its 10 Minutes. This value is also set in zone.properties in $IAS_ORACLE_HOME/Apache/Jserv where number mentioned is in milli second i.e. 600000 (equal to 10 Minutes) session.timeout = 600000.
Eg. Session Timeout is in minutes, so ICX session timeout=480 is 8Hrs.