My group is moving to a new Windows Server (Windows Server 2016). We need to migrate existing code without re-compiling. The existing code (on old Server 2008) utilizes Oracle 11g and 12c clients 32 and 64 bit. Mostly Unmanaged (Oracle.DataAccess.Client) clients but some use managed clients (Oracle.ManagedDataAccess.Client).
Can I install all of these clients in the GAC so that the applications will select the correct one?
If you really managed to install Oracle 11g and 12c clients 32 and 64 bit and ODP.NET Managed Driver and all of them are working, then you can be proud of yourself.
ODP.NET Managed Driver (Oracle.ManagedDataAccess.Client) is independent from all others, you an just install it.
It is not needed to install more than one version (i.e. one each for 32-bit and 64-bit). So, just install version 12 and you are done.
Unless you force a specific version (see How to load specific version of assembly from GAC) you have the Publisher policy which redirects to the installed version.
In case you install Oracle client 12.2 or never, have a look at SSMA unable to find specified provider
