Databases Reference
In-Depth Information
Resolving Oracle Net Service Names
With older versions of Oracle Net, you could use any of the following options to resolve
the service name the client specifies into the host and instance names needed to reach
an Oracle Database:
Local name resolution
For local name resolution, you install a file called
TNSNAMES.ORA
on each client
machine that contains entries that provide the host and Oracle instance for each
Oracle Net alias. You must maintain this file on the client machines if any changes
are made to the underlying database locations. Your network topology is almost
certain to change over time, so use of this option can lead to an increased mainte‐
nance load. If you are using Oracle Internet Directory or other centralized direc‐
tories, described later in this section, you do not need a
TNSNAMES.ORA
file. This
method is known as local naming.
Oracle Names service
Oracle Names was supported in earlier Oracle releases, providing a way to eliminate
the need for a
TNSNAMES.ORA
file on each client. That was the good part. The
bad part was that Oracle Names was a proprietary solution. Since Oracle Internet
Directory is based on standards and provides this functionality, Oracle declared
Oracle Names obsolete after the Oracle9
i
release.
Oracle Internet Directory or other LDAP directories
The need for a centralized naming service extends far beyond the Oracle environ‐
ment. In fact, there is a well-defined standard for accessing this type of information,
the Lightweight Directory Access Protocol (LDAP). As of the Oracle Database
11
g
release, Oracle Internet Directory (OID) is a part of Fusion. OID is an LDAP-
enabled directory that can fulfill the same role as the previously available Oracle
Names service. Since Oracle Database 10
g
, you can export directory entries to create
a local
TNSNAMES.ORA
file; this file may be used for clients not using the directory
or if the directory is unavailable. This method is known as directory naming.
Host naming
Clients can simply use the name of the host on which the instance runs. This is valid
for TCP/IP networks with a mechanism in place for resolving the hostname into
an IP address. For example, the Domain Name Service (DNS) translates a hostname
into an IP address, much as Oracle Names translates service names. Since Oracle
Database 10
g
, you can use this method with either a host name, domain-qualified
if appropriate, or a TCP/IP address, but the connection will not support advanced
services such as connection pooling. This method is known as Easy Connect.
