Before starting services on an Apps 11i instance, a DBA would first source the environment file which is typically the $APPL_TOP/APPSORA.env file. Apart from the 250 product tops, we have some environment variables which are available but not used very often:
CONTEXT_FILE : Gives the complete path of context file. You could do vi $CONTEXT_FILE.
CONTEXT_NAME: SID_hostname. Instead of doing an ls you could go straight to cd $APPLCSF/scripts/$CONTEXT_NAME
FND_SECURE: You could cd directly to FND_SECURE instead of FND_TOP/secure
FORMS60_OUTPUT defaults to $COMMON_TOP/temp