[Q] How does UNIX know where $ORACLE_HOME is?

Hi,

        This came up at work today and is pure curiosity. We all use $ORACLE_HOME (HP-UX server), but we don't have it in our .profiles. I've looked it up in the handbook, and it seems to be a mixture of /etc/oratab and the listener, but I still can't work out how the OS knows where ORACLE_HOME is.

Please help - it's going to niggle me until I find out.

Yours in anticipation

        Jo

The usual - anything I say reflects on me, and not upon my current employer.