How can i erase the default DCF record? because there already has a record. I needtake new DCF record to replace this default dcf record.
DCF records are stored in UTEST that is OTP area (one time programmable). You cannot erase it but you can program new record after the end (to be more precise replace stop record by new data record) and this latest records will apply.
See following document, 4.5. Disable MBIST and LBIST tests during startup BIST:
and Figure 56-8. Appending DCF records in device’s RM:
Retrieving data ...