Is it okay to have two oracle clients (both 11g and 12c) in the same db server? What are the potential issues I could face? The reason im doing this is to connect the app server where I'm deploying the clients to two databases each running on 11g and another on 12c.

  • I don't see any reason to have two Oracle Clients on one machine. You can connect with (almost) each Oracle client to (almost) each version of Oracle Server. For sure you should not get any issue with 11g vs. 12c version. The only reason to have two version is to have both 32 bit (x86) and 64 bit (x64) installed. Some components (e.g. Oracle OleDB) you cannot install more than once (per architecture) Jul 28, 2015 at 16:08
  • alright, then compatibility matrix says otherwise for using 11g client for 12c would'nt be possible?
    – tesla747
    Jul 28, 2015 at 16:33
  • Then install 12c only Jul 28, 2015 at 17:46
  • what happens if I install both the clients is my question/?
    – tesla747
    Jul 29, 2015 at 5:09
  • @tesla747 Can you provide a link where you found this information? That 11g and 12c are not compatible. Because they are.
    – Munchi
    Jul 29, 2015 at 10:57

1 Answer 1


You should not install more than one Oracle Client (per architecture) on one machine. For sure they do not work in parallel.

By heart I know several issues:

You would have to change PATH settings in order to determine which Client you want to use. TNS_ADMIN environment variable is used by both versions and must be set accordingly. Oracle OleDB provider can be installed only once (per architecture). Version of Oracle Data Provider for .NET (ODP.NET) must match the client version. Using ODBC can be also a challenge.

  • alright but then I can use my 11g client for my 12c DB as well right?
    – tesla747
    Jul 29, 2015 at 14:43
  • No, that is wrong or do you have some references to Oracle documentation that confirms this statements. In Database Client Installation Guide for Microsoft Windows one can read : "You can install all Oracle components in multiple Oracle homes on the same computer. However, some components can only support one active instance at a time. (...)"
    – miracle173
    Jul 29, 2015 at 16:30
  • Yes an 11g client can connect to a 12c Oracle server without any problem Jul 29, 2015 at 19:07

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