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常用的在线备库搭建有Rman auxiliary 和Rman备份集恢复两种方式。
（一）在环境配置OK的问题下，使用一条Rman命令就可以完成备库初始化同步，比较简单。# 登陆rman target sys/Oracle123@orcl_pri auxiliary sys/Oracle123@orcl_dg# 开始搭建辅助数据库RMAN>duplicate target database for standby nofilenamecheck from active database;
（二）
Rman备份集恢复的步骤相对多一些，但也不是很复杂。（1）规划数据库参数| DB | db_name | db_unique_name | tnsname |
|---|---|---|---|
| primary | orcl | orcl | orcl_pri |
| standby | orcl | orcl_s | orcl_dg |
| DB | db_file_base | log_file_base |
|---|---|---|
| primary | /oradata/orcl | /oradata/log |
| standby | /oradata/orcl_dg | /oradata/log_dg |
（2）主库参数配置（不考虑failover，只配置最少的参数）
alter system set log_archive_config = 'dg_config=(orcl,orcl_s)';alter system set log_archive_dest_2 = 'SERVICE=orcl_dg ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=orcl_s' scope=both;alter system set log_archive_dest_state_2 = ENABLE;alter system set standby_file_management = auto;# 生成pfile，作为备库启动的参数文件create pfile=/home/oracle/pfile.ora' from spfile;
（3）备库直接修改pfile.ora参数，并启动至nomount状态
*.db_unique_name='center_s'*.log_archive_dest_1='location=/oradata/log_dg'*.log_archive_dest_2='SERVICE=orcl_pri ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=orcl'*.db_file_name_convert='/oradata/orcl','/oradata/orcl_dg'*.log_file_name_convert='/oradata/log','/oradata/log_dg'# 启动数据库create spfile from pfile='/home/oracle/pfile.ora'startup nomount
（4）tnsnames.ora 和 listener.ora配置
（5）主库备份，上传至备库# 全备库RMAN> run { allocate channel t1 type disk; backup database FORMAT '/oradata/backup/data_%T_%s'; release channel t1;}# 控制文件备份RMAN> backup current controlfile for standby format '/oradata/backup/control.bak'; （5）备库恢复数据库
# 恢复控制文件RMAN> RESTORE STANDBY CONTROLFILE FROM '/oradata/backup/control.bak';# 启动数据库到mount状态RMAN> sql 'alter database mount'# 恢复数据库RMAN> catalog start with '/oradata/backup/';RMAN> restore database;RMAN> recover database;# 恢复有报错，可以忽略RMAN-00571: ===========================================================RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============RMAN-00571: ===========================================================RMAN-03002: failure of recover command at 10/17/2017 09:33:30RMAN-06054: media recovery requesting unknown archived log for thread 1 with sequence xx and starting SCN of xxxx
（6）创建备库standby日志文件，用于实时同步数据
alter system set standby_file_management = manual;ALTER DATABASE ADD standby LOGFILE group 11 '/oradata/log_dg/std11.log' size 500m ;ALTER DATABASE ADD standby LOGFILE group 12 '/oradata/log_dg/std12.log' size 500m ;ALTER DATABASE ADD standby LOGFILE group 13 '/oradata/log_dg/std13.log' size 500m ;ALTER DATABASE ADD standby LOGFILE group 14 '/oradata/log_dg/std14.log' size 500m ;
（7）开始实时日志应用并打开数据库
select open_mode ,flashback_on,current_scn from v$database;# 应用日志alter database recover managed standby database disconnect from session;# 查看应用状态，并在主库切换日志，查看序列变化select max(sequence#),applied,archived from v$archived_log group by applied,archived;# 打开数据库alter database recover managed standby database cancel;alter database open;alter database recover managed standby database disconnect from session using current logfile;
Oracle DG是数据库架构中最常用的一种，一定要能熟练搭建DG环境和掌握DG failover /switchover 、recovery的方式。
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