How can I apply LIMIT to this Block?

Hi All,

    The following script works fine for small number of records like upto 1 million records.
 
     when I try to load for 20 million records, the process ran out of memory error is occured.

      How can I apply LIMIT to this statement?
 
      and How can I implement cursor to this logic?

      Please Help me.
 
declare
      
  start_time  number;
  end_time   number;
 
  type T_MSISDN is table of TO2_MOBILE_DETAIL_STG.MSISDN%type;
  type T_ACTIVE is table of TO2_MOBILE_DETAIL_STG.ACTIVE%type;
  type T_ICCID is table of  TO2_MOBILE_DETAIL_STG.ICCID%type;
  type T_CUSTOMER_ID is table of TO2_MOBILE_DETAIL_STG.CUSTOMER_ID%type;
  type T_IS_PREPAID is table of TO2_MOBILE_DETAIL_STG.IS_PREPAID%type;
  type T_IMSI is table of TO2_MOBILE_DETAIL_STG.IMSI%type;
  type T_CONTRACT_ID is table of TO2_MOBILE_DETAIL_STG.CONTRACT_ID%type;

  L_MSISDN T_MSISDN;
  L_ACTIVE T_ACTIVE;
  L_ICCID T_ICCID;
  L_CUSTOMER_ID T_CUSTOMER_ID;
  L_IS_PREPAID T_IS_PREPAID;
  L_IMSI T_IMSI;
  L_CONTRACT_ID T_CONTRACT_ID;
 
begin

      start_time := DBMS_UTILITY.get_time;
      
  select MSISDN,
             ACTIVE,
             ICCID,
             CUSTOMER_ID,
             IS_PREPAID,
             IMSI,
             CONTRACT_ID
 bulk collect into
             L_MSISDN,
             L_ACTIVE,
             L_ICCID,
             L_CUSTOMER_ID,
             L_IS_PREPAID,
             L_IMSI,
             L_CONTRACT_ID
                        
      from TO2_MOBILE_DETAIL_STG;

  FORALL i in L_MSISDN.first .. L_MSISDN.last
 
    insert into to2_mobile_detail(MSISDN,ACTIVE,ICCID,CUSTOMER_ID,IS_PREPAID,IMSI,CONTRACT_ID)
      values
      (l_msisdn(i),l_active(i),l_iccid(i),TO_NUMBER(l_customer_id(i)),l_is_prepaid(i),l_imsi(i),TO_NUMBER(l_contract_id(i)));
      
    --dbms_output.put_line(L_MSISDN(i) || ', ' || L_ACTIVE(i));

            
            end_time := DBMS_UTILITY.get_time;
            DBMS_OUTPUT.PUT_LINE( ' Time took ' || to_char((end_time-start_time)/60));
 
end;
/

Thanks & Regards,
Ravi Ch.