配置standby redo log

Data Guard在最大保护和最高可用性模式下，Standby数据库必须配置standby redo log，通过下面的实验展示创建的原则和过程。

1.原则
1).standby redo log的文件大小与primary 数据库online redo log 文件大小相同
2).standby redo log日志文件组的个数依照下面的原则进行计算
   Standby redo log组数公式>=(每个instance日志组个数+1)*instance个数
   例如在我的环境中，只有一个节点，这个节点有三组redo，所以
   Standby redo log组数公式>=(3+1)*1 == 4
   所以需要创建4组Standby redo log
3).每一日志组为了安全起见，可以包含多个成员文件

2.配置过程，正常情况下仅需要在Standby端进行配置，考虑到主备切换，在primary端亦进行配置
1）Standby库添加四组Standby redo log，用户备库的恢复
sys@ora10g> alter database add standby logfile group 4 ('/oracle/u02/ORA10GDG/STANDBYRD01.LOG') size 200M;

Database altered.

sys@ora10g> alter database add standby logfile group 5 ('/oracle/u02/ORA10GDG/STANDBYRD02.LOG') size 200M;

Database altered.

sys@ora10g> alter database add standby logfile group 6 ('/oracle/u02/ORA10GDG/STANDBYRD03.LOG') size 200M;

Database altered.

sys@ora10g> alter database add standby logfile group 7 ('/oracle/u02/ORA10GDG/STANDBYRD04.LOG') size 200M;

Database altered.

2）Primary库添加四组Standby redo log，用于主备切换
sys@ora10g> alter database add standby logfile group 4 ('/oracle/u02/ORA10G/STANDBYRD01.LOG') size 200M;

Database altered.

sys@ora10g> alter database add standby logfile group 5 ('/oracle/u02/ORA10G/STANDBYRD02.LOG') size 200M;

Database altered.

sys@ora10g> alter database add standby logfile group 6 ('/oracle/u02/ORA10G/STANDBYRD03.LOG') size 200M;

Database altered.

sys@ora10g> alter database add standby logfile group 7 ('/oracle/u02/ORA10G/STANDBYRD04.LOG') size 200M;

Database altered.

3.Standby redo log删除方法
sys@ora10g> alter database drop standby logfile group 4;
sys@ora10g> alter database drop standby logfile group 5;
sys@ora10g> alter database drop standby logfile group 6;
sys@ora10g> alter database drop standby logfile group 7;

4.通过V$STANDBY_LOG视图验证standby redo log文件组是否成功创建
sys@ora10g> SELECT GROUP#,THREAD#,SEQUENCE#,ARCHIVED,STATUS FROM V$STANDBY_LOG;

    GROUP#    THREAD# SEQUENCE# ARC STATUS
---------- ---------- ---------- --- ----------
         4          0          0 YES UNASSIGNED
         5          0          0 YES UNASSIGNED
         6          0          0 YES UNASSIGNED
         7          0          0 YES UNASSIGNED

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