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用户反映修改密码后程序明显变慢，查看AWR发现:
ASH信息如下：
进一步验证:
SQL>select event,p1 from v$session t where t.username is not null and t.status=‘ACTIVE‘;
EVENT P1
---------------------------------------------------------------- ----------
row cache lock 7
row cache lock 7
row cache lock 7
row cache lock 7
查询v$rowcache
SQL> select parameter from v$rowcache where cache#=7;
PARAMETER
--------------------------------
dc_users
dc_users
dc_users
经查阅资料，在10.2.0.5及以后版本，使用错误密码登陆尝试会导致很高的Library Cache Locks或row cache lock，可以设置Oracle的隐含参数28401来避免：
alter system set event=‘28401 trace name context forever,level 1‘ scope=spfile;
通过审计功能分析是哪台机器哪个用户的频繁登陆失败
select * from (select os_username, userhost, terminal, username, count(*) cnt from dba_audit_trail where returncode = 1017 and timestamp >= date ‘2015-12-13‘ group by os_username, userhost, username, terminal order by 5 desc) where rownum < 10;
有时我们一台机器上部署了多个应用（服务），需要确认是哪一个进程在使用错误的密码访问Oracle，这里我们可以借助Oracle的数据库触发器记录日志
create table tmp_logon_denied ( id varchar2(36), ip varchar2(50), osuser varchar2(100), loginuser varchar2(100), machine varchar2(100), program varchar2(100), timestamp date, primary key (id) ); / CREATE OR REPLACE TRIGGER logon_denied_to_alert AFTER servererror ON DATABASE DECLARE message VARCHAR2(168); ip VARCHAR2(15); v_os_user VARCHAR2(80); v_module VARCHAR2(50); v_action VARCHAR2(50); v_pid VARCHAR2(10); v_sid NUMBER; v_program VARCHAR2(48); BEGIN IF (ora_is_servererror(1017)) THEN -- get ip FOR remote connections : IF upper(sys_context(‘userenv‘, ‘network_protocol‘)) = ‘TCP‘ THEN ip := sys_context(‘userenv‘, ‘ip_address‘); END IF; SELECT sid INTO v_sid FROM sys.v_$mystat WHERE rownum < 2; SELECT p.spid, v.program INTO v_pid, v_program FROM v$process p, v$session v WHERE p.addr = v.paddr AND v.sid = v_sid; v_os_user := sys_context(‘userenv‘, ‘os_user‘); dbms_application_info.read_module(v_module, v_action); message := to_char(SYSDATE, ‘YYYYMMDD HH24MISS‘) || ‘ logon denied from ‘ || nvl(ip, ‘localhost‘) || ‘ ‘ || v_pid || ‘ ‘ || v_os_user || ‘ with ‘ || v_program || ‘ – ‘ || v_module || ‘ ‘ || v_action; --sys.dbms_system.ksdwrt(2, message); insert into tmp_logon_denied(id, ip, osuser, loginuser, machine, program, timestamp) select sys_guid(), ip, t.OSUSER, t.USERNAME, t.MACHINE, t.PROGRAM, sysdate from v$session t where t.SID = v_sid; END IF; END; /
Oracle11g的delayed failed logins特性引起的性能问题
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原文地址：http://www.cnblogs.com/zhaoguan_wang/p/5042820.html
