Yes - if you use the old tnsnames connection syntax. This does not mean that oracle 11g is being used to connect though and you don't have to provide the "sde:oracle11g", just the instance "Dev" in your case. Adding "sde:oracle12c" is incorrect and is expected to fail. The easiest and best solution is to just use the newer syntax of "server/orainstance" (or another valid easy connect syntax detailed in the help: Database connections in ArcMap—Help | ArcGIS Desktop ).
Hi Michael, will you try connecting using the ez connect syntax, please? Make sure on the server you are connecting to the sqlnet.ora file has EZCONNECT specified within the NAMES.DIRECTORY_PATH parameter, and then use server/servicename in the instance parameter. See this blog post by Melissa Jarman: Easy Connect – Connecting to ArcSDE just got easier!
Does this work for you?
We replaced our 11.2 client with 12.1 client and it works fine, aside from some squirrel-ly PL/SQL syntax nuances we had to fix (object arrays)
-Jim
James:
Can you provide a screenshot of what your Oracle SDE connection properties look like in ArcCatalog, specifically the Instance that is saved?