The dbms_audit_mgmt package offers various ways to clear the audit trail.

For example, to remove logs created more than 365 days ago, you can:

- Use set_last_archive_timestamp to set this date
- Run clean_audit_trail to remove these

Like so:

begin
  dbms_audit_mgmt.set_last_archive_timestamp (
    audit_trail_type     =>  dbms_audit_mgmt.audit_trail_unified,
    last_archive_time    =>  systimestamp - 365
  );

  dbms_audit_mgmt.clean_audit_trail (
    audit_trail_type        => dbms_audit_mgmt.audit_trail_unified,
    use_last_arch_timestamp => true
  );
end;
/

If you have a large number of audit records to remove, this can take a long time. So it may be best to submit this as a job.

For more details, see the docs https://docs.oracle.com/database/121/DBSEG/audit_admin.htm#DBSEG90934