dump area

From: yashiro <noumian_at_yahoo.fr>
Date: Tue, 12 Aug 2008 00:52:34 -0700 (PDT)
Message-ID: <69e8ba6b-0a81-4408-8481-54106206d8ce@c65g2000hsa.googlegroups.com>

Hello every one
am usint oracle 11g on win2003.
i have warning on the OEM : "96% of background dump area is used".

What is the init param controlling the size on the dump area? How can i delete the trace files using OEM or SQLPLUS. (i dont want to delete them manually)