A couple of weeks ago, I had a problem whereby connection to the database was failing. I got the following error message in listener.log on the server:

TNS-12540 TNS:internal limit restriction exceeded
Cause: Too many TNS connections open simultaneously.
Action: Wait for connections to close and retry.

After some investigation, I thought it had to be one of two things...

The obvious one: I had unwitingly set a limit on the number of TNS connections allowed

or: There is a maximum number of dedicated server processes that can be spawned

Does anyone know how to increase either of these? I take it there is no overhead in doing so, only that more server processes\TNS connections will be generated.

P.S. We did toy with the idea that it could have been that we had exceeded LICENCE_MAX_SESSION (????), but increasing that didn't make any difference.