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隐含参数_disable_logging的几点说明
链接：https://www.eygle.com/archives/2006/06/more_about_disable_logging.html
在很久以前,曾经介绍过Oracle的一个内部隐含参数_disable_logging,看到有朋友论述这个参数,今天忍不住做一点补充说明.
1.当然,隐含有风险,设置请谨慎.
2.最初在9.2.0.6 Solaris版本上,设置该参数会触发Bug:3868748 使得数据库无法启动.
从警告日志中,通常可以获得的错误提示是:
| ORA-07445: exception encountered: core dump [kcrfwcint()+1625] [SIGFPE] [Integer divide by zero] [0x828739D] [] [] |
但是好在这个参数是动态的,在存在Bug版本中,我们可以修改数据库当前值来进行测试:
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SQL> alter system set "_disable_logging"=true scope=memory; System altered. |
3.这个Bug的影响范围并非全部,9.2.0.6之下,Oracle9.2.0.5,Oracle9.2.0.4等,都不受这个Bug影响.Oracle声称的修正该Bug的版本是Oracle10gR2(我未验正).
4.这个参数在Oracle9.2.0.4版本的Linux/Solaris上是不存在这个Bug的.在我的环境中经过验证,过程请参考(附注1).
5.在归档模式下,设置该参数会导致日志文件损坏.因为在设置该参数与归档原则违背，归档进程无法识别该日志文件格式，会将该日志文件标记为损坏.所以需要谨慎测试,具体请参考(附注2).
附注1:Solaris Oracle9.2.0.4设置测试过程:
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$ sqlplus "/ as sysdba" SQL*Plus: Release 9.2.0.4.0 - Production on Thu Apr 13 22:51:24 2006 Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
SQL> show parameter disa NAME TYPE VALUE System altered. SQL> shutdown immediate; Total System Global Area 286755168 bytes NAME TYPE VALUE BANNER |
附注2:归档模式下,该参数会导致日志文件损坏.
设置该参数后,切换日志:
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SQL> archive log list; System altered. SQL> select group#,status from v$Log; GROUP# STATUS SQL> show parameter disable NAME TYPE VALUE |
此时可以在警告日志中看到日志损坏的错误信息:
| Thu Apr 13 23:33:25 2006 ARC0: Evaluating archive log 2 thread 1 sequence 23 ARC0: Beginning to archive log 2 thread 1 sequence 23 Creating archive destination LOG_ARCHIVE_DEST_1: '/opt/oracle/oradata/conner/archive/1_23.dbf' ARC0: Log corruption near block 3849 change 0 time ? ARC0: All Archive destinations made inactive due to error 354 Thu Apr 13 23:33:25 2006 Errors in file /opt/oracle/admin/conner/bdump/conner_arc0_21506.trc: ORA-00354: corrupt redo log block header ORA-00353: log corruption near block 3849 change 0 time 04/13/2006 21:13:03 ORA-00312: online log 2 thread 1: '/opt/oracle/oradata/conner/redo02.log' ARC0: Archiving not possible: error count exceeded ARC0: Failed to archive log 2 thread 1 sequence 23 ARCH: Archival stopped, error occurred. Will continue retrying Thu Apr 13 23:33:26 2006 ORACLE Instance conner - Archival Error ARCH: Connecting to console port... Thu Apr 13 23:33:26 2006 ORA-16038: log 2 sequence# 23 cannot be archived ORA-00354: corrupt redo log block header ORA-00312: online log 2 thread 1: '/opt/oracle/oradata/conner/redo02.log' ARCH: Connecting to console port... ARCH: Thu Apr 13 23:33:26 2006 ORA-16038: log 2 sequence# 23 cannot be archived ORA-00354: corrupt redo log block header ORA-00312: online log 2 thread 1: '/opt/oracle/oradata/conner/redo02.log' |
历史上的今天...
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By eygle on 2006-06-20 11:27 | Comments (0) | Internal | 797 |