How to address ORA-03113? If I leave sqlplus open and unused for too long (probably 15 minutes or more), when I EXIT the following message will appear.

ORA-03113: end-of-file on communication channel


Does this indicate a real problem? If so, how might one go about correcting it?

There are a number of other posts about this error at database startup time. This is not at startup time. This is on the client. I can immediately start sqlplus again and have a working connection. Environment is Oracle 11.2.0.3.0 on Windows 64-bit, client is Windows 7 64-bit.
This is a generic error.

If you receive this in an active session while running some query, PL/SQL code or other statements, you should check the alert log of the database for further information. Usually it is caused by critical errors such as ORA-07445 that cause the server process that belongs to your session to terminate unexpectedly.

But if you receive this error in and idle session after a specific amount of time, as in your case, then do not worry, because it is absolutely normal when the database enforces an inactivity timeout, for example in the case of DRCP (Database Resident Connection Pooling).

Here is an example:

Database Resident Connection Pool (DRCP)