I'm working on AR-JDBC support for Oracle. The easiest way to do this for me is to run Oracle XE inside Windows XP in Parallels. That works fine. Except for this dreaded message that started showing up and killing all my efforts: “ORA-12519, TNS:no appropriate service handler found”. I love Oracle error messages. They are so incredibly helpful!
At least in this case I found a solution to the problem on da Internet. I'm writing this blog post to make the information more obvious to Google.
It seems there is a bug in Oracle XE in the monitoring of processes that manifests this way. Nice. But you can fix it! Just open up your SQL console, write "connect system", submit your password and then write "ALTER SYSTEM SET PROCESSES=150 SCOPE=SPFILE;". After that, remember to restart the listener. And everything should be joy again.