Oracle 11g、12c大量錯誤登陸嘗試帶來的資料庫異常

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APPLIES TO:

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

CAUSE

A hang is possible in earlier versions of RDBMS as a result of an unpublished bug fixed in the following versions:    12.1.0.1 (Base Release)    11.2.0.2 (Server Patch Set)    11.1.0.7 Patch 42 on Windows Platforms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 passwordEven 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 AUTHENTICATIONThis 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 unconditionallyIn 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 ;

小結：
關於大量的並發的錯誤密碼串連資料庫可能會導致資料庫hang、或者引起效能問題，對資料庫的影響非常大，近期就遇到過這樣的一個案例。當然Oracle本身這個特性是非常好的，但是在當下確實會遇到一些問題，大家可以使用event 28401禁用這個特性。但是最好是要從管理上解決掉這樣的問題，從安全層面做好管控。

Oracle 11g、12c大量錯誤登陸嘗試帶來的資料庫異常