If you don’t need both clients installed, then the simplest solution would be to uninstall the Oracle 11 client. If you need both, read on.
Sometimes Toad has problems if:
- start Toad, make a connection using one Oracle home.
- end the connection, but leave Toad open.
- make another connection with a different Oracle home
If this is what’s happening for you, try closing Toad completely on step 2.
On the other hand, if you just start Toad and try to connect the first time with the Oracle 12 client, and get the error right away, maybe changing path would solve that.
To change path:
- In windows, click Start, then rt-click on ‘Computer’ and choose ‘Properties’
- in the window that appears, click ‘advanced system settings’
- in the next dialog that appears, click on the ‘advanced’ tab.
- click ‘environment variables’
- find ‘path’ in the ‘system variables’ box.
- edit the path so that the version 12 client comes before the version 11 client.
Click OK on all the dialogs, then try Toad again.