The problem is that we have to upgrade to Win 2012 and Oracle 11g is not compatible - only 12.2 is.
I doubt that. Generally, Oracle clients and servers are compatible with a major version difference of at least 1, i.e. Client 11 and Server 12 or vice versa. A major version difference of 2 should still work. At least, it was so for decades. I remember using C8 with S10 and C9 with S11, also C11 with S10.
Alexander
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Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)