Oracle 11g r2 standard edition installation - set environment variable PATH and create tnsnames.ora I have installed Oracle 11g R2 standard edition (server software, 2GB download from Oracle).

I found that the 'Environment Variable PATH' has not been set. Which of these directory should I use for the PATH value:- 


Oracle base
Software location
Database file location


Also do I need to create 'TNS_ADMIN' environment variable and 'TNSNAMES.ora' file

Kindly advice. Thank you
Normally you use the oraenv script to set you environment correctly for a given ORACLE_SID. The ORACLE_SID and ORACLE_HOME combinations are maintained in /etc/oratab or /var/opt/oracle/oratab which is read by the oraenv script that should be sourced (called with a .)

What oraenv by default sets does is make sure that PATH contains at least $ORACLE_HOME/bin

If you want to have some control over where your SQL*net files are located it is smart to create a TNS_ADMIN environment variable that points to the directory where amongst others tnsnames.ora is located. The tnsnames.ora file is most important to be able to point to a - local or remote - database using SQL*net.

If you only access your database from the same machine as where the database is running and you do not access an other database, a tnsnames.ora is not needed, just convenient. Normally we have a tnsnames.ora that contains lots of database on the site.