ORA-19821故障分析

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标题：ORA-19821故障分析

作者：惜分飞©版权所有[未经本人同意,不得以任何形式转载,否则有进一步追究法律责任的权利.]

数据库报错
数据库启动报ORA-00283和ORA-19821错

SQL> recover database;
ORA-00283: recovery session canceled due to errors
ORA-19821: an intentionally corrupt log file was found
SQL> recover datafile 1;
ORA-00283: recovery session canceled due to errors
ORA-19821: an intentionally corrupt log file was found

Thu May 03 12:06:51 2018
Recovery of Online Redo Log: Thread 1 Group 1 Seq 1 Reading mem 0
  Mem# 0: D:\APP\SOHTDB\ORADATA\xifenfei\REDO01.LOG
Media Recovery failed with error 19821
Errors in file d:\app\sohtdb\diag\rdbms\xifenfei\xifenfei\trace\xifenfei_pr00_660.trc:
ORA-00283: recovery session canceled due to errors
ORA-19821: an intentionally corrupt log file was found
Slave exiting with ORA-283 exception
Errors in file d:\app\sohtdb\diag\rdbms\xifenfei\xifenfei\trace\xifenfei_pr00_660.trc:
ORA-00283: recovery session canceled due to errors
ORA-19821: an intentionally corrupt log file was found
ORA-283 signalled during: ALTER DATABASE RECOVER  database  ...

ORA-19821报错原因
这个错误相对比较少见，查询mos，由于设置了_disable_logging = TRUE导致该问题
ORA-19821

检查alert日志,_disable_logging参数确实被认为设置为true了.
_disable_logging

解决方法
根据官方的描述,这样的情况无法常规恢复,但是我们知道设置这个参数是为了不产生日志,因此出现这种情况,只能通过隐含参数,禁止数据库进行实例恢复,强制打开数据库.在这样的过程中非常容易遭遇类似ORA-600 2662的错误.
_disable_logging_mos

设置这个参数是为了不产生日志，当数据库非干净关闭(主机断电，数据库crash，shutdown abort等）,就非常可能导致数据库无法正常启动.***千不可万不能在生产环境中设置_disable_logging = TRUE***
参考文档:Ora-19821 during the recovery (Doc ID 1217143.1)
Init.ora Parameter “_DISABLE_LOGGING” [Hidden] Reference Note (Doc ID 29552.1)

ORA-600 2662

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标题：ORA-600 2662

作者：惜分飞©版权所有[未经本人同意,不得以任何形式转载,否则有进一步追究法律责任的权利.]

在数据库恢复中,ORA-600 2662我想是很多人都非常熟悉的错误,下文是对于该错误的一些解释
ORA-600 2662解释说明

ERROR:
  Format: ORA-600 [2662] [a] [b] {c} [d] [e]
VERSIONS:
  versions 6.0 to 12.1
DESCRIPTION:
  A data block SCN is ahead of the current SCN.
  The ORA-600 [2662] occurs when an SCN is compared to the dependent SCN
  stored in a UGA variable.
  If the SCN is less than the dependent SCN then we signal the ORA-600 [2662]
  internal error.
ARGUMENTS:
  Arg [a]  Current SCN WRAP
  Arg [b]  Current SCN BASE
  Arg {c}  dependent SCN WRAP
  Arg [d]  dependent SCN BASE
  Arg [e]  Where present this is the DBA where the dependent SCN came from.

出现ORA-600 2662可能的原因

  (1) doing an open resetlogs with _ALLOW_RESETLOGS_CORRUPTION enabled
  (2) a hardware problem, like a faulty controller, resulting in a failed
      write to the control file or the redo logs
  (3) restoring parts of the database from backup and not doing the
      appropriate recovery
  (4) restoring a control file and not doing a RECOVER DATABASE USING BACKUP
      CONTROLFILE
  (5) having _DISABLE_LOGGING set during crash recovery
  (6) problems with the DLM in a parallel server environment
  (7) a bug

ORA-600 2662解决方法

   (1) if the SCNs in the error are very close, attempting a startup several
       times will bump up the dscn every time we open the database even if
       open fails. The database will open when dscn=scn.
   (2)You can bump the SCN either on open or while the database is open
      using Event:ADJUST_SCN
      Be aware that you should rebuild the database if you use this
      option.