密码延迟验证导致的系统HANG住-创新互联

出處 http://yangtingkun.net/?p=1429
又是一个11g新特性导致的问题。
这个新特性很早之前就研究过，也在其他客户处碰到过类似的问题。从11g开始，如果一个用户使用不正确的密码尝试登录数据库，那么随着登录失败次数的增加，每次登录验证前延迟等待的时间也会增加：

SQL> SET TIME ON 18:30:54 SQL> 18:30:58 SQL> conn test/test
Connected. 18:31:25 SQL> 18:31:25 SQL> conn test/a
conn test/a
conn test/a
conn test/a
conn test/a
conn test/a
conn test/a
conn test/test
conn test/a
ERROR:
ORA-01017: invalid username/password; logon denied
Warning: You are no longer connected TO ORACLE. 18:31:26 SQL> ERROR:
ORA-01017: invalid username/password; logon denied 18:31:26 SQL> ERROR:
ORA-01017: invalid username/password; logon denied 18:31:26 SQL> ERROR:
ORA-01017: invalid username/password; logon denied 18:31:27 SQL> ERROR:
ORA-01017: invalid username/password; logon denied 18:31:29 SQL> ERROR:
ORA-01017: invalid username/password; logon denied 18:31:32 SQL> ERROR:
ORA-01017: invalid username/password; logon denied 18:31:36 SQL> Connected. 18:31:36 SQL> ERROR:
ORA-01017: invalid username/password; logon denied
Warning: You are no longer connected TO ORACLE. 18:31:36 SQL>