[Oracle]隐含参数_disable_logging的几点说明

ZDNet软件频道　时间：2008-09-22　作者：盖国强 | 开发者在线　我要评论()
本文关键词：隐含参数盖国强 Oracle Oracle

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。

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:

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:

$ sqlplus "/ as sysdba"

SQL*Plus: Release 9.2.0.4.0 - Production on Thu Apr 13 22:51:242006

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production

SQL> show parameter disa

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
_disable_logging boolean FALSE
SQL> alter system set "_disable_logging"=true scope=both;

System altered.

SQL> shutdown immediate;
Database closed.
Database dismounted.
Oracleinstance shut down.
SQL> startup
Oracleinstance started.

Total System Global Area 286755168 bytes
Fixed Size                   731488 bytes
Variable Size             167772160 bytes
Database Buffers          117440512 bytes
Redo Buffers                 811008 bytes
Database mounted.
Database opened.
SQL> show parameter disable

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
_disable_logging boolean TRUE
SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
PL/SQL Release 9.2.0.4.0 - Production
CORE 9.2.0.3.0 Production
TNS for Solaris: Version 9.2.0.4.0 - Production
NLSRTL Version 9.2.0.4.0 - Production

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:

SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            /opt/Oracle/oradata/conner/archive
Oldest online log sequence     20
Next log sequence to archive   23
Current log sequence           23
SQL> alter system switch logfile;

System altered.

SQL> select group#,status from v$Log;

    GROUP# STATUS
---------- ----------------
         1 INACTIVE
         2 ACTIVE
         3 INACTIVE
         4 CURRENT

SQL> show parameter disable

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
_disable_logging boolean TRUE

此时可以在警告日志中看到日志损坏的错误信息:

Thu Apr 13 23:33:252006
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 23:33:252006
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 04/13/200621:13:03
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 23:33:262006
OracleInstance conner - Archival Error
ARCH: Connecting to console port...
Thu Apr 13 23:33:262006
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 23:33:262006
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"

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