Log rotation of diag logs? In on of our Oracle 11.2.0 installations the directory database\diag\rdbms\$DB\$DB\alert is filled with hundreds of xml files (log.xml, log1.xml ...). Can Oracle be configured to do log rotation there? And where are these files used?
Oracle won't do this natively. You'll have to use an external utility to do this.

On Unix systems this is usually achieved with logrotate.