You read a few postings on how to connect MOSS to oracle database, and you concluded that the installation and configuration of oracle client should take less than 30 minutes; After you search for oracle driver, registered at Oracle site to download “appropriate” driver, after a few dry runs, you realized oracle client driver installation which was supposed to take only 30 minutes is now running into a couple of hours; If you are caught in this merry-go round, the following steps are for you…
1. Download ODAC10202.exe or ODTwithODAC10202.exe into a temporary folder. Please note: Do not download this file into the “Tmp” directory.
2. Unzip its contents by running the executable.
3. In the directory where you unzip ODAC10202.exe, an install directory is created.
4. Run the Oracle Universal Installer (OUI) by launching the setup.exe within the “install” directory that was unzipped.
4. OUI will lead you through the installation on your machine. After the installation, you may delete ODAC10202.exe and the temporary installation folders and files.
5. A Net service name allows an Oracle client to use a simple alias to connect to the database server. The alias definition contains all the information needed to create a connection.
6. To create an alias, launch Net Configuration Assistant from Windows Start Menu –> All Programs –> Oracle – <Oracle Home> –> Configuration and Migration Tools. Follow these instructions to create a net service name as a shortcut for the data source value in your connection string.
7. To avoid any error, copy the tnsnames in UAT and place it under <%Install Directory%>:\Oracle\product\10.2.0\client_2\NETWORK\ADMIN
Please see the screens below for OUI Step by step screen. And test your connectivity to the oracle database. First, use the famous PING to verify physical layer connectivity to the Oracle database. Then use tnsping to verify connectivity to Oracle database
Note: On the screen below, select the first option.
Note: In Step 7, the path in textbox two below is the Oracle path. Look for the ADMIN directory in the path and place your tnsnames.Ora file. 
Note: Verify that all these options below are selected
Sample tnsname.ora file…..
TTTUAT_HOSTNAME.TT.COM=
(DESCRIPTION=
(ADDRESS=
(PROTOCOL=TCP)
(HOST=167.32.54.20)
(PORT=1566)
)
(CONNECT_DATA=
(SERVER=dedicated)
(SID=TTUAT)
)
