1.    架构

在Oracle 10g 中，传输日志到备用节点数据库的进程为ARCH 和LGWR 。（在11g 中，LGWR 被LNS 替代，但10g 中是不是LGWR 我不确定！）

在备用节点上通过参数log_archive_config 、fal_client 和fal_server 接收日志，并和主节点通讯，标识该日志是否被应用。

Data Guard 采用最大可用模式，保证数据实时同步到最少一个节点上。因为我们选择第一个备用节点作为数据实时同步点，同步进程采用LGWR 进程。

2.    配置

在一个主节点两个备用节点的Data Guard 10g 的环境中，各个节点的初始化参数的主要配置项。

在主节点的初始化参数文件配置：

*.log_archive_config='dg_config=(codb,codg,codg2)'
*.log_archive_dest_1='location=/oradata/htcodb/archive_logs_codb'
*.log_archive_dest_2='service=codb_standby lgwr sync affirm  valid_for=(online_logfiles,primary_role) db_unique_name=codg'
*.log_archive_dest_3='service=codb_standby2 arch async affirm  valid_for=(online_logfiles,primary_role) db_unique_name=codg2'
*.log_archive_dest_state_2='enable'
*.log_archive_dest_state_3='enable'

在备用节点一的初始化参数文件配置：

*.db_name='codb'
*.db_unique_name='codg'
*.fal_client='code_standby'
*.fal_server='codb_primary'
*.log_archive_config='dg_config=(codb,codg,codg2)'
*.log_archive_dest_1='location=/oradata/archivelog/ valid_for=(all_logfiles,all_roles) db_unique_name=codg'
*.log_archive_format='%t_%s_%r.dbf'

在备用节点二的初始化参数文件配置：

*.db_name='codb'
*.db_unique_name='codg2'
*.fal_client='codb_standby'
*.fal_server='codb_primary'
*.log_archive_config='dg_config=(codb,codg2)'
*.log_archive_dest_1='location=/u01/archivelog_standby/ valid_for=(all_logfiles,all_roles) db_unique_name=codg2'
*.log_archive_format='%t_%s_%r.dbf'

主节点和备用节点之间的通讯是通过Oracle Net 实现的。在参数fal_client 和fal_server 上就用到Oracle Net 中的配置信息。

在主节点的tnsnames.ora 文件中，关于DG 的配置项如下所示：

CODB_PRIMARY =
 (DESCRIPTION =
   ( ADDRESS = (PROTOCOL = TCP)(HOST = codb1-vip.htsc.com.cn)(PORT = 1521))
  (ADDRESS = (PROTOCOL = TCP)(HOST = codb2-vip.htsc.com.cn)(PORT = 1521))
  (LOAD_BALANCE = yes)
  (CONNECT_DATA =
    (SERVER = DEDICATED)
    (SERVICE_NAME = codb)
  )
 )-

CODB_STANDBY =
 (DESCRIPTION =
  (ADDRESS_LIST =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.15.219)(PORT = 1521))
  )
  (CONNECT_DATA =
    (SID = codb)
  )
 )

CODB_STANDBY2 =
 (DESCRIPTION =
  (ADDRESS_LIST =
    (address = (protocol = tcp)(host = 192.168.15.90)(port = 1521))
  )
  (CONNECT_DATA =
    (SID = codb)
  )
 )

在备用节点一的tnsnames.ora 文件中，关于DG 的配置项如下所示：

CODB_PRIMARY =
 (DESCRIPTION =
  (ADDRESS = (PROTOCOL = TCP)(HOST = codb1-vip.htsc.com.cn)(PORT = 1521))
  (ADDRESS = (PROTOCOL = TCP)(HOST = codb2-vip.htsc.com.cn)(PORT = 1521))
  (LOAD_BALANCE = yes)
  (CONNECT_DATA =
    (SERVER = DEDICATED)
    (SERVICE_NAME = codb)
  )
 )

CODB_STANDBY =
 (DESCRIPTION =
  (ADDRESS_LIST =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.15.219)(PORT = 1521))
  )
  (CONNECT_DATA =
    (SERVICE_NAME = codb)
  )
 )

在备用节点二的tnsnames.ora 文件中，关于DG 的配置项如下所示：

CODB_PRIMARY =
 (DESCRIPTION =
  (ADDRESS = (PROTOCOL = TCP)(HOST = codb1-vip.htsc.com.cn)(PORT = 1521))
  (ADDRESS = (PROTOCOL = TCP)(HOST = codb2-vip.htsc.com.cn)(PORT = 1521))
  (LOAD_BALANCE = yes)
  (CONNECT_DATA =
    (SERVER = DEDICATED)
    (SERVICE_NAME = codb)
  )
 )

CODB_STANDBY =
 (DESCRIPTION =
  (ADDRESS_LIST =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.15.90)(PORT = 1521))
  )
  (CONNECT_DATA =
    (SERVICE_NAME = codb)
  )
 )

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