Oracle Client on Windows Introduction
About the Oracle Client for Windows:
The Oracle Client is what connects your applications with your database. Almost all client side applications use it. Generally applications will either use the Oracle Client directly (such as our SQL tool Golden) or will use a connectivity option such as ODBC, OLEDB, .Net, JDBC, etc, which use the Oracle Client "under the hood". Most applications that use the Oracle Client directly will scan your machine to find the Oracle Client.
Oracle recommends using an Oracle Client version that matches the highest Oracle database version that you need to connect to. Using older clients to connect to newer database versions can cause issues (one of which is that older clients will not understand newer datatypes such as timestamps.)
The Oracle Client can be installed from various Oracle installation media or can be downloaded from Oracle's Technology Network web site.
Which Client to use, 32bit or 64bit:
If the client application that you wish to use is a 32bit application, then it must use the 32bit Oracle Client. If the client application is a 64bit application then it must use the 64bit Oracle Client. If you need to use both 32bit and 64bit applications, then you will be installing both the 32bit and 64bit Oracle Client.
Full Oracle Client or the Oracle Instant Client:
The full Oracle Client can be installed from various Oracle installation media (disc or downloads) and is installed using the Oracle Installer. This method is a good choice if you'd prefer to be prompted for various options regarding the connectivity options that you need. This option creates an Oracle Home and registers it with Windows so that client applications can find it.
If you know exactly what options you need, a good choice is the Oracle Instant Client. The Instant Client is a set of smaller zip files containing the Oracle Client files along with some installation scripts to use if you need ODBC drivers installed. This method does not create an official Oracle Home and does not register itself with Windows. This can be very useful if you have a primary Oracle Home of one "bitness" (let's say a 64bit Oracle Client) and want to add a 32bit Oracle Client for your 32bit applications to use. Most client applications (such as our applications) allow you to choose the Oracle Client to connect to without putting it into the system path or affecting your primary Oracle Home in any way.