Creating a new data source for websphere/JAS

We have an as400 enterprise server and websphere/jas on an NT platform. We wish to connect to a file within an Oracle Database an a Sun box.
We have successfully created a new data source definition (type O) and connected to the file via UTB from a fat client. However this does not work from out html/JAS server.
In order to get this to work I assume that we have to
1. uncomment the line
"O=oracle.jdbc.driver.OracleDriver "
within our JAS.INI file.
2. Create a TNSNAMES.ORA file (remember this is a AS400 install so at the moment this is blank)
3. Copy the relavant odbc oracle class files to our JAS server.
The question I have, is that I don't know the format of our TNSNAMES.ORA file. Does somebody have some examples that I can look at.
Thanks in advance.
Chriss.

This is an example of part of my tnsnames.ora file - the host can also be an IP address, the SID is the database connect string.

owsys=
(DESCRIPTION =
(ADDRESS = (PROTOCOL= TCP)(Host= *******)(Port= 1525))
(CONNECT_DATA = (SID = *******))
)
sbldvpep=
(DESCRIPTION =
(ADDRESS = (PROTOCOL= TCP)(Host= ********)(Port= 1525))
(CONNECT_DATA = (SID = ********))

Hope this helps.

Thanks Cleo,
I'll try this.
Regards
Chriss