- Download the appropriated instant client (for ArcGIS Server use x64 version)
- Create a folder on the local hard drive (write down the path)
- Unzip the instant client in the folder in step 2
- Assuming windows, edit the 'PATH' variable and add Step #2's path to the variable
- Restart ArcGIS service
- Create your direct connect connection:
- Register the connection with server
Now you can use the sde connection for any map document, geoprocessing service, etc...
This workflow will be valid for desktop instant client setup, except it should be noted that the 64-bit version should be before the 32-bit reference path.