A configuration file that contains net service names mapped to connect descriptors. This file is used for the local naming method.
The tnsnames.ora file must reside in one of the following locations:
The directory specified
by the TNS_ADMIN
environment variable If the TNS_ADMIN
environment variable is not defined as a variable on Windows NT, it may
be in the registry.
The node's global configuration
directory. For Sun Solaris, this directory
is /var/opt/oracle
. Windows NT does not have a central directory.
The $ORACLE_HOME/network/admin
directory on UNIX or the ORACLE_HOME\network\admin
directory on Windows operating systems.