After some time using Toad (not sure what's causing this), the "Connect Using Oracle Client" CheckBox becomes disabled:
After a restart of Toad it is enabled again:
BR
Dirk
The checkbox is only enabled when no connection is made
So you can't connect different sessions with different modes?
Not at the same time, no. All active connections have to be with the same client (or all with no client).
Is there a reason why you want to mix and match?
Not at the moment. So that's ok with me.
Maybe this behavior should be documented at the CheckBox. Otherwise I'm probably not the last one to ask this question 
Good idea. You are probably right.