Oracle configuration file tips
Article by author Steve Callan
| This article
deals with knowing how to set a location for
your tnsnames.ora file and where to look for
that location (having a "good" file and
"accepting" its use because you know where it is
or how to find it). The ubiquitous Oracle user
name Scott just received a promotion: he is a
newly anointed junior DBA who must set up his
company's 100 computers to use Oracle. Scott
knows he has a good tnsnames.ora file, and he
wants to use it as a template for everyone else.
One huge misconception about using Oracle
products that occurs among other-than-RDBMS
users (novice Forms developers in particular)
has to do with the proper configuration of the
non-RDBMS Oracle product.
Every Oracle product has its own set of
"Oracle network" configuration files. Each
Oracle product has its own ORACLE_HOME. Within
those ORACLE_HOME locations is a directory named
network, and within the network directory, you
will find a directory named admin. This is where
Oracle installs the Oracle Net configuration
files, including tnsnames.ora. Like many other
things in Oracle, if Oracle puts it there,
Oracle expects to find it there, unless you
happen to intervene. In this case, intervention
can be a good thing.
Where does Oracle expect to find the
tnsnames.ora file? The table below shows some of
the possible locations.
|
UNIX platforms |
Windows platforms |
|
ORACLE_HOME\network\admin |
ORACLE_HOME/network/admin |
|
/var/opt/oracle |
No counterpart |
|
A .tnsnames file in your
home directory |
No counterpart |
|
In the directory
specified by the TNS_ADMIN environment
variable |
In the directory
specified by the TNS_ADMIN environment
variable or registry setting |
When Scott needs to add a new database
(service identifier, etc.) for employees to use,
or change a host name, all he needs to do is
edit one file: the tnsnames.ora file found in
the directory specified by the TNS_ADMIN
variable. The change is immediately available to
everyone. UNIX users can place the environment
variable in logon or resource files (for
example, C-shell users can use "setenv TNS_ADMIN
/some/location" in the .cshrc file; other shells
can have it exported, and so on). Where do
Windows users place or set the variable?
I mentioned the "Registry" word earlier, but
only because I wanted to be technically correct.
Oracle's documentation even mentions placing the
TNS_ADMIN variable in the "R" word location. But
really, what possible reason would you want to
use the "Registry" for something like that?
There is no need to; and, in fact, you can find
other documents from Oracle that discourage the
use of directly editing the registry. Which, by
the way, is good advice, and it happens to match
Microsoft's admonition about directly editing
the registry. So, the answer for Windows users:
set TNS_ADMIN as an environment variable, either
at the system or user level.
Suppose you have a user who uses SQL*Plus and
Form Builder from Forms 6i. Each product creates
its own set of configuration files in their
respective ORACLE_HOME-network-admin directories
(substitute / or \ for the hyphen, depending on
the platform). Simply "direct" both Oracle
products to use the tnsnames.ora file found in
the directory specified by the TNS_ADMIN
environment variable. The solution to the "What
gives?" question posted on numerous web sites is
that simple.
In closing, the other configuration file
frequently used in conjunction with the
tnsnames.ora file (sqlnet.ora) can also be
placed in the same directory specified by the
TNS_ADMIN environment variable. Whether you
choose to use sqlnet.ora is a separate issue;
there is no general absolute requirement to use
it, but there are many cases where it is useful
and necessary.
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