以前看到资料，自己做完测试后，就结束了，时间长了就忘记，现在每次做完实验，都记录下来。

客户端1 :
SQL> select * from v$mystat where rownum = 1 ;

       SID STATISTIC#      VALUE
---------- ---------- ----------
       130          0          0


begin
for i in 1 .. 500000 loop
   update gaolu01 set lname = 'jerry' where id = 1 ;
   commit;
  end loop;
end;
/

客户端 2 ：

SQL> select * from v$mystat where rownum = 1 ;

       SID STATISTIC#      VALUE
---------- ---------- ----------
        70          0          0



declare
  m_name varchar2(50);
begin
  for i in 1..500000 loop
     select lname into  m_name from gaolu01  where id = 1 ;
  end loop;
end;
/


declare
  m_name varchar2(50);
begin
  for i in 1..500000 loop
     select lname into  m_name from gaolu01  where id = 1 ;
  end loop;
end;
/

客户端3 ：
select sid,event,total_waits,time_waited_micro from v$session_event where event in('log buffer
space','buffer busy waits') and sid in(130,70);

       SID EVENT                                                            TOTAL_WAITS TIME_WAITED_MICRO
---------- ---------------------------------------------------------------- ----------- -----------------
        70 buffer busy waits                                                     111513           3238741
       130 buffer busy waits                                                        488              3373

SQL>

就是 读的时候   buffer busy waits   更多。 相对 写的时候 。