create table {tablename}_his as select * from {tablename} where ...

alter index {indexname} unusable;

declare  
   cursor mycursor is SELECT  ROWID FROM {tablename} WHERE ltl_time < to_date('2017-08-01','YYYY-mm-dd') order by rowid;  
   type rowid_table_type is  table  of rowid index by pls_integer;
   v_rowid   rowid_table_type;
BEGIN
   open mycursor;
   loop
     fetch   mycursor bulk collect into v_rowid  limit 5000;   --------每次处理5000行，也就是每5000行一提交
     exit when v_rowid.count=0;
     forall i in v_rowid.first..v_rowid.last
        delete from {tablename} nologging  where rowid=v_rowid(i);
     commit;
   end loop;
   close mycursor;
END;

• 重建索引

alter index {indexname} rebuild;