Oracle 11g、12c大量錯誤登陸嘗試帶來的資料庫異常

Oracle Database - Enterprise Edition - Version 10.2.0.5 and later
Information in this document applies to any platform.           

A hang is possible in earlier versions of RDBMS as a result of an unpublished bug fixed in the following versions:

    12.1.0.1 (Base Release)
    11.2.0.2 (Server Patch Set)
    11.1.0.7 Patch 42 on Windows Platforms           

Document 9776608.8 Bug 9776608 - Hang from concurrent login to same account with a wrong password

Even with this fix, numerous failed logins attempts can cause row cache lock waits and/or library cache lock waits. 

This was reported in:

Bug 11742803 LOTS OF 'LIBRARY CACHE LOCK' DURING USER LOGON AUTHENTICATION
This was closed as not a bug because there is an intentional wait when a login fails.           

SOLUTION

In Oracle 11g Release 11.1.0.7,  the wait is disabled unconditionally
In Oracle 11g Release 2 and higher, in order to disable the wait between login failures the event 28401 needs to be explicitly enabled:
The event can be set as follows:

alter system set event ="28401 TRACE NAME CONTEXT FOREVER, LEVEL 1" scope=spfile;

To unset the event, set as follows:
SQL> Alter system set event= '28401 trace name context off' scope=spfile ;