环境：

　　Oracle 11.2.0.2 RAC for IBM AIX 6.1 2节点

　　一条简单的修改用户密码SQL语句 ：

　　alter user ** identified by ***;

　　竟然会挂住在那，此时所有的客户端(.net架构短连接)均无法连接，也是连接出不来，也不报错。

　　此时做了个10046，生成了个跟踪文件如 附件。

　　后重启了2个节点数据库后，用了不到5分钟，又出现所有客户端无法连接数据库。

　　FYI:

　　相关BUG

　　Description

　　In 11g there is an intentional delay between allowing failed logon

　　attempts to retry. For some specific application types this can cause

　　a problem as the row cache entry is locked for the duration of the

　　delay . This can lead to excessive row cache lock waits for DC_USERS

　　for specific users / schemas .

　　This "fix" allows the logon delay to be disabled in 11.2.0.1 onwards

　　by setting event 28401 in the init.ora.

　　eg:

　　event="28401 trace name context forever, level 1" # disable logon delay.

　　This "event" will disable the logon sleep delay system-wide,

　　ie. it will affect all user accounts, system-wide, and so should be used

　　with extreme caution.

　　Example scenario:

　　A mix of correct and incorrect logon attempts occur for user X

　　On each successive failed login attempt the failed logon count

　　is incremented for user X.

　　Without this fix (without the event set):

　　After 3 successive failures a sleep delay is introduced starting

　　at 3 seconds and extending to 10 seconds max. During each delay

　　the user X row cache lock is held in exclusive mode preventing

　　any concurrent logon attempt as user X (and preventing any

　　other operation which would need the row cache lock for user X).

　　With the fix (with the event set):

　　There is no sleep delay.

　　In either scenario the configured logon profile rules are still

　　applied (eg: The profile option FAILED_LOGIN_ATTEMPTS is still

　　honoured and so if the account becomes locked due to exceeeding

　　this FAILED_LOGIN_ATTEMPTS then further attempts to

　　log in will then correctly fail immediately with no delay).






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