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HomeDatabaseMysql TutorialOracle 归档模式archivelog

Oracle数据库有联机重做日志,这个日志是记录对数据库所做的修改,比如插入,删除,更新数据等,对这些操作都会记录在联机重做日

查看Oracle数据库是否为归档模式

  1.select name,log_mode from v$database;
  NAME LOG_MODE
  ------------------ ------------------------

  QUERY NOARCHIVELOG


  2.使用ARCHIVE LOG LIST 命令
  Database log mode No Archive Mode
  Automatic archival Disabled
  Archive destination /data/oracle/product/10.2.0/db_1//dbs/arch
  Oldest online log sequence 739
  Current log sequence 741

什么是Oracle归档模式

Oracle数据库有联机重做日志,这个日志是记录对数据库所做的修改,比如插入,删除,更新数据等,对这些操作都会记录在联机重做日志里。一般数据库至少要有2个联机重做日志组。当一个联机重做日志组被写满的时候,就会发生日志切换,这时联机重做日志组2成为当前使用的日志,当联机重做日志组2写满的时候,又会发生日志切换,去写联机重做日志组1,就这样反复进行。


如果数据库处于非归档模式,联机日志在切换时就会丢弃. 而在归档模式下,当发生日志切换的时候,被切换的日志会进行归档。比如,当前在使用联机重做日志1,当1写满的时候,发生日志切换,开始写联机重做日志2,这时联机重做日志1的内容会被拷贝到另外一个指定的目录下。这个目录叫做归档目录,拷贝的文件叫归档重做日志。  

数据库使用归档方式运行时才可以进行灾难性恢复。

  1.归档日志模式和非归档日志模式的区别
  非归档模式只能做冷备份,并且恢复时只能做完全备份.最近一次完全备份到系统出错期间的数据不能恢复.
  归档模式可以做热备份,并且可以做增量备份,可以做部分恢复.
  用ARCHIVE LOG LIST 可以查看当前模式状态时归档模式还是非归档模式.

配置数据库的归档模式

  1.改变非归档模式到归档模式:
  1)SQL> conn / as sysdba (以DBA身份连接数据库)
  2)SQL> shutdown immediate; (立即关闭数据库)
  3)SQL> startup mount (启动实例并加载数据库,,但不打开)
  4)SQL> alter database archivelog; (更改数据库为归档模式)
  5)SQL> alter database open; (打开数据库)
  6)SQL> alter system archive log start; (启用自动归档)
  7)SQL> exit (退出)

  做一次完全备份,因为非归档日志模式下产生的备份日志对于归档模式已经不可用了.这一步非非常重要!


  2.改变归档模式到非归档模式:
  1)SQL>SHUTDOWN NORMAL/IMMEDIATE;
  2)SQL>STARTUP MOUNT;
  3)SQL>ALTER DATABASE NOARCHIVELOG;

  4)SQL>ALTER DATABASE OPEN;


  3.启用自动归档: LOG_ARCHIVE_START=TRUE
  归档模式下,日志文件组不允许被覆盖(重写),当日志文件写满之后,如果没有进行手动归档,那么系统将挂起,知道归档完成为止.
  这时只能读而不能写.
  运行过程中关闭和重启归档日志进程
  SQL>ARCHIVE LOG STOP

  SQL>ARCHIVE LOG START


  4.手动归档: LOG_ARCHIVE_START=FALSE
  归档当前日志文件
  SQL>ALTER SYSTEM ARCHIVE LOG CURRENT;
  归档序号为052的日志文件
  SQL>ALTER SYSTEM ARCHIVE LOG SEQUENCE 052;
  归档所有日志文件
  SQL>ALTER SYSTEM ARCHIVE LOG ALL;
  改变归档日志目标
  SQL>ALTER SYSTEM ARCHIVE LOG CURRENT TO '&PATH';
  5.归档模式和非归档模式的转换
  第4步的逆过程.
  6.配置多个归档进程
  Q:什么时候需要使用多个归档进程?
  A:如果归档过程会消耗大量的时间,那么可以启动多个归档进程,这是个动态参数,可以用ALTER SYSTEM动态修改.
  SQL>ALTER SYSTEM SET LOG_ARCHIVE_MAX_PROCESSES=10;
  Oracle9i中最多可以指定10个归档进程
  与归档进程有关的动态性能视图
  v$bgprocess,v$archive_processes
  7.配置归档目标,多归档目标,远程归档目标,归档日志格式
  归档目标 LOG_ARCHIVE_DEST_n
  本地归档目标:
  SQL>LOG_ARCHIVE_DEST_1 = "LOCATION=D:ORACLEARCHIVEDLOG";
  远程归档目标:
  SQL>LOG_ARCHIVE_DEST_2 = "SERVICE=STANDBY_DB1";
  强制的归档目标,如果出错,600秒后重试:
  SQL>ALTER SYSTEM SET LOG_ARCHIVE_DEST_4 = "LOCATION=E:ORACLEARCHIVEDLOG MANDATORY REOPEN=600";
  可选的归档目标,如果出错,放弃归档:
  SQL>ALTER SYSTEM SET LOG_ARCHIVE_DEST_3 = "LOCATION=E:ORACLEARCHIVEDLOG OPTIONAL";
  归档目标状态:关闭归档目标和打开归档目标
  关闭归档目标1
  SQL>ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_1 = DEFER
  打开归档目标2
  SQL>ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2 = ENABLE
  归档日志格式
  LOG_ARCHIVE_FORMAT
  8.获取归档日志信息
  V$ARCHIVED_LOG
  V$ARCHIVE_DEST
  V$LOG_HISTORY
  V$DATABASE
  V$ARCHIVE_PROCESSES
  ARCHIVE LOG LIST;

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