The ORACLE_HOME environment variable must define the Oracle software
installation path.
The ORACLE_SID environment variable can be used to define the
name of the local database instance.
The PATH environment variable must define the access path to database
client programs.
On UNIX™, LD_LIBRARY_PATH (or equivalent) must hold the
path to $ORACLE_HOME/lib.
The Oracle® client library
'ORACLE_HOME/lib/libclntsh*' must be available.
The TNSNAMES.ORA file must define the database server identifiers for remote connections (the
Oracle Listener must be started on the
database server to allow remote connections).
The SQLNET.ORA file must define network settings for remote connections.