Ask about FGA in 11gR1

 Hi,

   My db server (11gR1 on Linux 64) was enabled FGA by a DBA (and now he's leave this position). In my db, some tables were audit by use the DBMS_FGA.ADD_POLICY. I can select from dba_fga_audit_trail table to view operations from all of users. But now, size of table is large (it contains multi records) and I want delete amount of records that base on the Timestamp field. I can delete them manual or create job scheduler to delete them.

  I want ask Oracle support some parameters to delete them automatically (so I need not write my job scheduler) ? I just read some documents about FGA and know Oracle supports store records as XML file format (with AUDIT_TRAIL = xml) but if I store audit records as xml file, how is it effect to my db persomance ??