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[Mysql数据库] Oracle 11g、12c大量错误登陆尝试带来的数据库异常

发表于 2018-1-24 08:00:01

APPLIES TO:

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

  1. A hang is possible in earlier versions of RDBMS as a result of an unpublished bug fixed in the following versions:
  2. 12.1.0.1 (Base Release)
  3. 11.2.0.2 (Server Patch Set)
  4. 11.1.0.7 Patch 42 on Windows Platforms
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  1. Document 9776608.8 Bug 9776608 - Hang from concurrent login to same account with a wrong password
  2. Even with this fix, numerous failed logins attempts can cause row cache lock waits and/or library cache lock waits.
  3. This was reported in:
  4. Bug 11742803 LOTS OF 'LIBRARY CACHE LOCK' DURING USER LOGON AUTHENTICATION
  5. This was closed as not a bug because there is an intentional wait when a login fails.
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SOLUTION
  1. In Oracle 11g Release 11.1.0.7, the wait is disabled unconditionally
  2. In Oracle 11g Release 2 and higher, in order to disable the wait between login failures the event 28401 needs to be explicitly enabled:
  3. The event can be set as follows:
  4. alter system set event ="28401 TRACE NAME CONTEXT FOREVER, LEVEL 1" scope=spfile;
  5. To unset the event, set as follows:
  6. SQL> Alter system set event= '28401 trace name context off' scope=spfile ;
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小结:
关于大量的并发的错误密码连接数据库可能会导致数据库hang、或者引起性能问题,对数据库的影响非常大,近期就遇到过这样的一个案例。当然Oracle本身这个特性是非常好的,但是在当下确实会遇到一些问题,大家可以使用event 28401禁用这个特性。但是最好是要从管理上解决掉这样的问题,从安全层面做好管控。



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