准备工作:
 create table t as select * from all_objects ;
 
 1: 一次commit;
  declare
    vn_count int ;
  begin
      vn_count := dbms_utility.get_cpu_time;
      update t
      set CREATED = sysdate;   
      commit;
      dbms_output.put_line(dbms_utility.get_cpu_time-vn_count||'ms');
  end ;
 out:  35ms
 
 
 2: 分批次commit ;
   declare                                                           
       vn_count int ;                                                
       nn          number(10);                                       
       cursor cur_1 is                                               
         select rowid row_id,t.* from t t;                           
   begin                                                             
       vn_count := dbms_utility.get_cpu_time;                        
       for vc_cur in cur_1 loop                                      
           update t                                                  
           set created = sysdate                                     
           where rowid = vc_cur.row_id;                              
           nn := nn+1;                                               
           if nn > 100 then                                          
               commit;                                               
               nn  := 0;                                             
           end if;                                                   
       end loop;                                                     
       commit;                                                       
       dbms_output.put_line(dbms_utility.get_cpu_time-vn_count||'ms');
   end ;     
          
  out:   146ms
                                               

分批次更新之所以执行的时间比较长感觉是因为产生了一致性读