Did you upgrade to reach to WLS 9.2?
Do you have a default authenticator as well?
So long you have a default authenticator and the control flag of the rdbms authenticator is not set to required/requisite other applications will not be affected.
Why don't you get rid of your compatability realm? it would require only a few changes in config n file..
You can set up a new rdbdms authenticator following my article here
Let me know if you face any issues