You could do inside the mapper if you wanted.
The key is to write a little .net component to do exactly what you want. Might take in an input (such as database name) and return a boolean. I’d put all the configuration stuff either hardcoded for now or inside a config file.
It’s easy to test out using a Windows Form.
Then, you just have to GAC it and you can then call it using a Scripting Functoid or call is inside an Orchestration.
I’d just look at MSDN for a sample of the code using the OracleClient.
Hope this helps.