I want to connect ArcGIS 10.6 to an Oracle 12c Enterprise Edition. However, I found different informations on the Esri websites on how to do so.

  1. I followed this website (http://desktop.arcgis.com/de/arcmap/latest/manage-data/gdbs-in-oracle/connect-oracle.htm) and executed it step by step. All worked fine, as far as I can tell. However, I got an Error message telling me that:

Failed to connect to specified server. Do you want to continue? Cannot connect to database because the database client software failed to load. Be sure the database client software is installed and configured correctly.

  1. I found this ESRI website https://desktop.arcgis.com/de/arcmap/latest/get-started/introduction/whats-new-in-arcgis.htm where it states that "Oracle Instant client will not work.", directly contradicting the instructions on website 1.

So what is right, respectivley, how can I connect ArcGIS 10.6 to Oracle 12c?

  • There is no contradiction. This refers to a special case of connectivity.
    – Vince
    Feb 28, 2019 at 11:07

1 Answer 1


I managed to establish a connection. 2 things I changed seemed to have made the difference.

  1. I installed the 64bit Instant Client of Oracle, assuming that on Windows 10 64bit and ArcGIS 64bit that would be the correct choice - which it isn't. For my setup, you have to install the 32bit version of the Oracle Instant Client.
  2. I changed the location of the tnsnames.ora file from C:/oracle/instantclient_12_2
    to C:/oracle/instantclient_12_2/network/admin
  • 3
    64-bit Instant Client would be correct for a 64-bit client (like ArcGIS Pro or Server), but you used a 32-bit client (ArcMap).
    – Vince
    Feb 28, 2019 at 11:09
  • I tried both Clients, but only when I use the 32bit Version I can connect from ArcMap @Vince. Any ideas why that might be the case?
    – blabbath
    Feb 28, 2019 at 11:12
  • 3
    ArcMap is a 32-bit client.
    – Vince
    Feb 28, 2019 at 11:19

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