How to set ORACLE_HOME Path in Unix and Linux?

ORACLE_HOME refers to either:

1. a directory where the Oracle software is installed; or
2. an environment variable pointing to the directory where the Oracle software is installed. 

Check current value:

echo The current ORACLE_HOME is %ORACLE_HOME%

Set the ORACLE_HOME environment variable:

set ORACLE_HOME=C:\oracle\ora10.2

Unix & Linux

Check current value:

env | grep ORACLE_HOME

Change the ORACLE_HOME environment variable (valid for bash and ksh):

export ORACLE_HOME=/app/oracle/product/10.2.0/db_1