Postgresql主从异步流复制方案 oracle数据库主从复制

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imking 2024-02-29 16:43:51

文章标签 Postgresql主从异步流复制方案数据库网络操作系统 oracle 文章分类 云原生云计算

前面章节说到mysql主从复制问题，本章节说说oracle的主从复制技术adg，这个也是业内大家用的最多的解决方案。

Data Gurad通过冗余数据来提供数据保护，Data Gurad 通过日志同步机制保证冗余数据和主数据之前的同步，这种同步可以是实时，延时，同步，异步多种形式。Data Gurad常用于异地容灾和小企业的高可用性方案，虽然可以在Standby机器上执行只读查询，从而分散Primary数据库的性能压力，但是Data Gurad决不是性能解决方案。

分类：

逻辑Standby接收后将其转换成SQL语句，在Standby数据库上执行SQL语句实现同步，这种方式叫SQL Apply。

物理Standby接收完Primary数据库生成的REDO数据后，以介质恢复的方式实现同步，这种方式也叫Redo Apply。

保护模式：

数据保护模式

Data Guard 允许定义3钟数据保护模式，分别是最大保护（Maximum Protection），最大可用（Maximum Availability）和最大性能（Maximum Performance）。

1. 最大保护（Maximum Protection）

这种模式能够确保绝无数据丢失。要实现这一步当然是有代价的，它要求所有的事务在提交前其REDO不仅被写入到本地的Online Redologs，还要同时写入到Standby数据库的Standby Redologs，并确认REDO数据至少在一个Standby数据库中可用（如果有多个的话），然后才会在Primary数据库上提交。如果出现了什么故障导致Standby数据库不可用的话（比如网络中断），Primary数据库会被Shutdown，以防止数据丢失。

使用这种方式要求Standby Database必须配置Standby RedoLog，而Primary Database必须使用LGWR，SYNC，AFFIRM方式归档到Standby Database.

2. 最高可用性（Maximum availability）

这种模式在不影响Primary数据库可用前提下，提供最高级别的数据保护策略。其实现方式与最大保护模式类似，也是要求本地事务在提交前必须至少写入一台Standby数据库的Standby Redologs中，不过与最大保护模式不同的是，如果出现故障导致Standby数据库无法访问，Primary数据库并不会被Shutdown，而是自动转为最高性能模式，等Standby数据库恢复正常之后，Primary数据库又会自动转换成最高可用性模式。

这种方式虽然会尽量避免数据丢失，但不能绝对保证数据完全一致。这种方式要求Standby Database 必须配置Standby Redo Log，而Primary Database必须使用LGWR，SYNC，AFFIRM 方式归档到Standby Database.

3. 最高性能（Maximum performance）

缺省模式。这种模式在不影响Primary数据库性能前提下，提供最高级别的数据保护策略。事务可以随时提交，当前Primary数据库的REDO数据至少需要写入一个Standby数据库，不过这种写入可以是不同步的。如果网络条件理想的话，这种模式能够提供类似最高可用性的数据保护，而仅对Primary数据库的性能有轻微影响。这也是创建Standby数据库时，系统的默认保护模式。

这种方式可以使用LGWR ASYNC 或者 ARCH 进程实现，Standby Database也不要求使用Standby Redo Log。

oracle 11g ADG实施手册

一、环境介绍

操作系统版本：RHEL LINUX 6.7(64位）

数据库版本：ORACLE 11GR2 11.2.0.4(64位）

IP地址规划：

主数据库

192.168.11.12

SID：pri

db_name:pri

db_unique_name：pri

主库主机名：ora11g

备份数据库

192.168.11.13

SID：std

db_name:pri

db_unique_name：std

备库主机名：ora11g-dg

版本统一、数据库统一、防火墙关闭

二、安装oracle

主库在安装完软件后需要进行DBCA建库操作，推荐不要启用归档模式，会节省时间，备库端不要建库！可以开启监听程序

三、开始搭建Dataguard

1：将数据库改为强制日志模式（此步骤只在主库上做）

查看当前是否强制日志模式：

SYS@pri> select name,log_mode,force_logging from v$database;   
NAME LOG_MODE FOR
---------         ------------ ---
PRI         NOARCHIVELOG NO
SYS@pri> alter database force logging;
Database altered.
SYS@pri> select name,log_mode,force_logging from v$database;
NAME LOG_MODE FOR
---------         ------------ ---
PRI         NOARCHIVELOG YES

2：创建密码文件（此步骤只在主库上做，一般数据库都）

将主库的密码文件copy给备库，并重命名

[oracle@pri dbs]$ scp orapwpri 192.168.11.13:$ORACLE_HOME/dbs/orapwstd

3：创建standby redolog日志组（此步骤只在主库上做）

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

假如只有一个节点，这个节点有三组redolog，

所以Standby redo log组数>=(3+1)*1 == 4

所以至少需要创建4组Standby redo log

由于已经存在group1-3,，所以group号只能从4开始

SYS@pri>
alter database add standby logfile group 4 '/u01/app/oracle/oradata/standbylog/std_redo04.log' size 50m;
alter database add standby logfile group 5 '/u01/app/oracle/oradata/standbylog/std_redo05.log' size 50m;
alter database add standby logfile group 6 '/u01/app/oracle/oradata/standbylog/std_redo06.log' size 50m;
alter database add standby logfile group 7 '/u01/app/oracle/oradata/standbylog/std_redo07.log' size 50m;

4：修改主库的pfile参数文件（此步骤只在主库上做）

用spfile创建一个pfile,用于修改：

SYS@pri> create pfile from spfile;

修改主库的pfile：

以下内容是需要新增加的：

*.db_unique_name='pri' DG主库和备库的db_name必须一致，db_unique_name不一致
*.log_archive_config='dg_config=(pri,std)' pri主数据库SID，std备份数据库SID
*.log_archive_dest_1='location=/u01/app/oracle/arch valid_for=(all_logfiles,all_roles) db_unique_name=pri' 主数据库的归档日志路径和SID
*.log_archive_dest_2='service=std valid_for=(online_logfiles,primary_role) db_unique_name=std' 备份数据库的SID
*.log_archive_dest_state_1=enable
*.log_archive_dest_state_2=enable
*.log_archive_max_processes=4
*.fal_server='std' 备份数据库的SID
*.fal_client='pri' 主数据库的SID
*.db_file_name_convert='/u01/app/oracle/oradata/std','/u01/app/oracle/oradata/pri' 第一个目录是备份数据库数据文件路径（备份服务器上有此目录），第二个是主数据库数据文件路径
*.log_file_name_convert='/u01/app/oracle/oradata/std','/u01/app/oracle/oradata/pri' 第一个目录是备份数据库数据文件路径（备份服务器上有此目录），第二个是主数据库数据文件路径
*.standby_file_management='auto'
修改完毕，保存退出
手工创建/u01/app/oracle/arch：       
[oracle@pri dbs]$ mkdir –p /u01/app/oracle/arch
5：用修改过的pfile重新创建一个spfile，用于重启数据库    （此步骤只在主库上做）
关闭数据库：
SYS@pri> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
用修改过的pfile重新创建一个spfile：
SYS@pri> create spfile from pfile;   
此时把数据库改为归档模式：        （如果当初建库时选择了启用归档，则此步骤忽略）
由于当前数据库已关闭，首先需要把数据库启动到mount状态
SYS@pri> startup mount;       
ORACLE instance started.
Database mounted.
SYS@pri> alter database archivelog;    启用归档模式
Database altered.
SYS@pri> alter database open;        OPEN数据库
Database altered.
SYS@pri> archive log list;            查看是否启用归档模式
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /u01/app/oracle/arch
Oldest online log sequence 22
Next log sequence to archive 24
Current log sequence 24
如上，归档路径已经改为/u01/app/oracle/arch，证明对pfile的修改已生效
查看当前数据库是否使用spfile启动：   
SYS@pri> show parameter spfile;
NAME TYPE VALUE
----------- ----------- -----------------------------------------------------------------
spfile string /u01/app/oracle/product/11.2.0/db_1/dbs/spfilepri.ora
如上，若能看到spfile的路径，则证明数据库是使用spfile启动的，若没有值，则说明是用pfile启动的。
确认数据库已经启用归档模式和强制日志模式：
SYS@pri> select name,log_mode,force_logging from v$database;
NAME LOG_MODE FOR
---------     ------------------- -------
PRI ARCHIVELOG YES
6：修改监听文件，添加静态监听        （主库、备库都要做）
主库：
[oracle@pri ~]$ cd $ORACLE_HOME/network/admin
[oracle@pri admin]$ vim listener.ora     添加的内容如下红色字体部分：
# listener.ora Network Configuration File: /u01/app/oracle/product/11.2.0/db_1/network/admin/listener.ora
# Generated by Oracle configuration tools.
LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.11.12)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = pri)
      (ORACLE_HOME = /u01/app/oracle/product/11.2.0/db_1)
      (SID_NAME = pri)
    )
  )
ADR_BASE_LISTENER = /u01/app/oracle
备库：
[oracle@pri ~]$ cd $ORACLE_HOME/network/admin
[oracle@pri admin]$ vim listener.ora     添加的内容如下红色字体部分：
# listener.ora Network Configuration File: /u01/app/oracle/product/11.2.0/db_1/network/admin/listener.ora
# Generated by Oracle configuration tools.
LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.11.13)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = std)
      (ORACLE_HOME = /u01/app/oracle/product/11.2.0/db_1)
      (SID_NAME = std)
    )
  )
ADR_BASE_LISTENER = /u01/app/oracle

使新增加的监听生效：（主库和备库端都要做）

[oracle@pri admin]$ lsnrctl stop
[oracle@pri admin]$ lsnrctl start

确认新增加的静态监听有效：

主库：

[oracle@pri ~]$ lsnrctl status
..........................................(N行省略)
Services Summary...
Service "pri" has 2 instance(s).
Instance "pri", status UNKNOWN, has 1 handler(s) for this service...
Instance "pri", status READY, has 1 handler(s) for this service...
Service "priXDB" has 1 instance(s).
Instance "pri", status READY, has 1 handler(s) for this service...
The command completed successfully
备库：
[oracle@std ~]$ lsnrctl status
..........................................(N行省略)
Services Summary...
Service "std" has 2 instance(s).
Instance "std", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
如上，静态监听添加成功
7：编辑网络服务名配置文件tnsnames.ora        （主库和备库端都要做）
[oracle@ora11g admin]$ pwd
/u01/app/oracle/product/11.2.0/db_1/network/admin
[oracle@ora11g admin]$ ls
listener.ora samples tnsnames.ora
listener.ora_bak shrept.lst tnsnames.ora_bak
[oracle@ora11g admin]$ more tnsnames.ora
# tnsnames.ora Network Configuration File: /u01/app/oracle/product/11.2.0/db_1/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.
pri =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.11.12)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = pri)
    )
  )
std =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.11.13)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = std)
    )
  )

保证主库和备库的tnsnames.ora文件中的内容完全相同，可以把修改后的文件直接传给备库。

[oracle@ora11g admin]$ scp tnsnames.ora 192.168.11.13:$ORACLE_HOME/network/admin
tnsnames.ora 100% 925 0.9KB/s 00:00

配置完后，确保在任意一端上都能tnsping通对方：

[oracle@pri admin]$ tnsping std
[oracle@std admin]$ tnsping pri
8：在备库端，修改pfile参数文件        （只在备库端做）
首先，在主库端把pfile拷贝给备库端的$ORACLE_HOME/dbs目录下，并重命名：
[oracle@ora11g-dg ~]$ cd $ORACLE_HOME/dbs
[oracle@ora11g-dg dbs]$ ls
hc_std.dat init.ora initstd.ora lkSTD orapwstd spfilestd.ora
[oracle@ora11g dbs]$ scp initpri.ora 192.168.11.13:$ORACLE_HOME/dbs/initstd.ora
initpri.ora 100% 1497 1.5KB/s 00:00
然后在备库端进行修改：
[oracle@ora11g-db ~]$ cd $ORACLE_HOME/dbs
[oracle@ora11g-dg dbs]$ more initstd.ora
pri.__db_cache_size=318767104
pri.__java_pool_size=4194304
pri.__large_pool_size=4194304
pri.__oracle_base='/u01/app/oracle'#ORACLE_BASE set from environment
pri.__pga_aggregate_target=335544320
pri.__sga_target=503316480
pri.__shared_io_pool_size=0
pri.__shared_pool_size=163577856
pri.__streams_pool_size=0
*.audit_file_dest='/u01/app/oracle/admin/std/adump'
*.audit_trail='db'
*.compatible='11.2.0.0.0'
*.control_files='/u01/app/oracle/oradata/std/control01.ctl','/u01/app/oracle/oradata/std/control02.ctl'
*.db_block_size=8192
*.db_domain=''
*.db_name='pri' DG主库和备库的db_name必须一致，db_unique_name不一致
*.db_recovery_file_dest='/u01/app/oracle/flash_recovery_area'
*.db_recovery_file_dest_size=4070572032
*.diagnostic_dest='/u01/app/oracle'
*.dispatchers='(PROTOCOL=TCP) (SERVICE=stdXDB)'
*.log_archive_format='%t_%s_%r.dbf'
*.memory_target=836763648
*.open_cursors=300
*.processes=150
*.remote_login_passwordfile='EXCLUSIVE'
*.undo_tablespace='UNDOTBS1'
以下需要手工添加：
*.db_unique_name='std'
*.log_archive_config='dg_config=(pri,std)'
*.log_archive_dest_1='location=/u01/app/oracle/arch valid_for=(all_logfiles,all_
roles) db_unique_name=std'
*.log_archive_dest_2='service=pri valid_for=(online_logfiles,primary_role) db
_unique_name=pri'
*.log_archive_dest_state_1=enable
*.log_archive_dest_state_2=enable
*.log_archive_max_processes=4
*.fal_server='pri'
*.fal_client='std'
*.db_file_name_convert='/u01/app/oracle/oradata/pri','/u01/app/oracle/oradata
/std'
*.log_file_name_convert='/u01/app/oracle/oradata/pri','/u01/app/oracle/oradat
a/std'
*.standby_file_management='auto'
修改完毕，保存退出
注意：整个搭建过程最需要留意的就是主库和备库的PFILE配置，建议修改完后仔细对照主备库PFILE的区别
9：在备库端手工创建所需的目录    （备库端做，不提前创建的话恢复时会报错！）
mkdir -pv /u01/app/oracle/admin/std/adump
mkdir -pv /u01/app/oracle/diag/rdbms/std/std/trace
mkdir -pv /u01/app/oracle/arch
mkdir -pv /u01/app/oracle/oradata/std
mkdir -pv /u01/app/oracle/oradata/standbylog
mkdir -pv /u01/app/oracle/flash_recovery_area
10：用修改后的pfile创建一个spfile，用于启动数据库        （备库端做）
[oracle@std ~]$ sqlplus / as sysdba
Connected to an idle instance.
SYS@std> create spfile from pfile;
File created.
将数据库启动到nomount状态：
SYS@std> startup nomount;
ORACLE instance started.
Total System Global Area 839282688 bytes
Fixed Size 2233000 bytes
Variable Size 482348376 bytes
Database Buffers 352321536 bytes
Redo Buffers 2379776 bytes
SYS@std>
11：利用RMAN在备库上恢复主库            （备库端做）
[oracle@std ~]$ rman target sys/oracle@pri auxiliary sys/oracle@std
Recovery Manager: Release 11.2.0.3.0 - Production on Tue Apr 15 16:39:28 2014
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database: PRI (DBID=775616459)
connected to auxiliary database: PRI (not mounted)
RMAN> duplicate target database for standby from active database nofilenamecheck;
这条命令可以直接恢复数据文件，standby控制文件，standby日志组，非常霸道
Starting Duplicate Db at 16-MAR-16
using target database control file instead of recovery catalog
allocated channel: ORA_AUX_DISK_1
channel ORA_AUX_DISK_1: SID=134 device type=DISK
contents of Memory Script:
{
backup as copy reuse
targetfile '/u01/app/oracle/product/11.2.0/db_1/dbs/orapwpri' auxiliary format
'/u01/app/oracle/product/11.2.0/db_1/dbs/orapwstd' ;
}
executing Memory Script
Starting backup at 16-MAR-16
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=140 device type=DISK
Finished backup at 16-MAR-16
contents of Memory Script:
{
backup as copy current controlfile for standby auxiliary format '/u01/app/oracle/oradata/std/control01.ctl';
}
executing Memory Script
Starting backup at 16-MAR-16
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
copying standby control file
output file name=/u01/app/oracle/product/11.2.0/db_1/dbs/snapcf_pri.f tag=TAG20160316T110737 RECID=2 STAMP=906635257
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:01
Finished backup at 16-MAR-16
contents of Memory Script:
{
sql clone 'alter database mount standby database';
}
executing Memory Script
sql statement: alter database mount standby database
contents of Memory Script:
{
set newname for tempfile 1 to
"/u01/app/oracle/oradata/std/temp01.dbf";
switch clone tempfile all;
set newname for datafile 1 to
"/u01/app/oracle/oradata/std/system01.dbf";
set newname for datafile 2 to
"/u01/app/oracle/oradata/std/sysaux01.dbf";
set newname for datafile 3 to
"/u01/app/oracle/oradata/std/undotbs01.dbf";
set newname for datafile 4 to
"/u01/app/oracle/oradata/std/users01.dbf";
backup as copy reuse
datafile 1 auxiliary format
"/u01/app/oracle/oradata/std/system01.dbf" datafile
2 auxiliary format
"/u01/app/oracle/oradata/std/sysaux01.dbf" datafile
3 auxiliary format
"/u01/app/oracle/oradata/std/undotbs01.dbf" datafile
4 auxiliary format
"/u01/app/oracle/oradata/std/users01.dbf" ;
sql 'alter system archive log current';
}
executing Memory Script
executing command: SET NEWNAME
renamed tempfile 1 to /u01/app/oracle/oradata/std/temp01.dbf in control file
executing command: SET NEWNAME
executing command: SET NEWNAME
executing command: SET NEWNAME
executing command: SET NEWNAME
Starting backup at 16-MAR-16
using channel ORA_DISK_1
channel ORA_DISK_1: starting datafile copy
input datafile file number=00001 name=/u01/app/oracle/oradata/pri/system01.dbf
output file name=/u01/app/oracle/oradata/std/system01.dbf tag=TAG20160316T110744
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:01:38
channel ORA_DISK_1: starting datafile copy
input datafile file number=00002 name=/u01/app/oracle/oradata/pri/sysaux01.dbf
output file name=/u01/app/oracle/oradata/std/sysaux01.dbf tag=TAG20160316T110744
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:01:09
channel ORA_DISK_1: starting datafile copy
input datafile file number=00003 name=/u01/app/oracle/oradata/pri/undotbs01.dbf
output file name=/u01/app/oracle/oradata/std/undotbs01.dbf tag=TAG20160316T110744
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:15
channel ORA_DISK_1: starting datafile copy
input datafile file number=00004 name=/u01/app/oracle/oradata/pri/users01.dbf
output file name=/u01/app/oracle/oradata/std/users01.dbf tag=TAG20160316T110744
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:01
Finished backup at 16-MAR-16
sql statement: alter system archive log current
contents of Memory Script:
{
switch clone datafile all;
}
executing Memory Script
datafile 1 switched to datafile copy
input datafile copy RECID=2 STAMP=906635463 file name=/u01/app/oracle/oradata/std/system01.dbf
datafile 2 switched to datafile copy
input datafile copy RECID=3 STAMP=906635463 file name=/u01/app/oracle/oradata/std/sysaux01.dbf
datafile 3 switched to datafile copy
input datafile copy RECID=4 STAMP=906635463 file name=/u01/app/oracle/oradata/std/undotbs01.dbf
datafile 4 switched to datafile copy
input datafile copy RECID=5 STAMP=906635463 file name=/u01/app/oracle/oradata/std/users01.dbf
Finished Duplicate Db at 16-MAR-16
RMAN>

恢复数据库结束

12：尝试开启备库

登陆并查看数据库当前状态：

[oracle@std ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on Tue Jan 14 16:41:50 2014
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SYS@std> startup
SYS@std> select status from v$instance;
STATUS

------------

MOUNTED （RMAN恢复完直接就是mount状态）

13：备库启动日志应用（启用备库前确认归档日志是否都已拷贝）

SYS@std> alter database recover managed standby database disconnect from session;

Database altered.

（停止日志应用的命令是：alter database recover managed standby database cancel;）

查看日志应用情况：

SYS@std> set pagesize 100
SYS@std> select sequence#,applied from v$archived_log order by 1;
SEQUENCE# APPLIED
---------- ---------
8 YES
9 YES
10 YES

如上，如果发现有个NO的，也是正常的，说明该日志在主库上还没有归档，可以在主库上运行alter system switch logfile;命令来进行日志切换，再到备库查看日志应用情况

14：分别查看主库和备库的归档序列号是否一致：

先在主库手动切换一下日志：

SYS@pri> alter system switch logfile;
System altered.

然后查看主库：

SYS@pri> archive log list;
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /u01/app/oracle/arch
Oldest online log sequence 22
Next log sequence to archive 24
Current log sequence 24

备库：
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /u01/app/oracle/arch
Oldest online log sequence 22
Next log sequence to archive 0
Current log sequence 24
结果完全一致，至此，DataGuard的搭建成功！
15：检查命令
查看standby启动的DG进程
SQL> select process,client_process,sequence#,status from v$managed_standby; 
PROCESS   CLIENT_P  SEQUENCE# STATUS 
--------- -------- ---------- ------------ 
ARCH      ARCH             23 CLOSING 
ARCH      ARCH              0 CONNECTED            //归档进程 
ARCH      ARCH             21 CLOSING 
ARCH      ARCH              0 CONNECTED 
RFS       ARCH              0 IDLE 
RFS       UNKNOWN           0 IDLE 
RFS       LGWR             24 IDLE               //归档传输进程 
RFS       UNKNOWN           0 IDLE 
MRP0      N/A              24 APPLYING_LOG      //日志应用进程 
9 rows selected. 
查看数据库的保护模式：
SQL> select database_role,protection_mode,protection_level,open_mode from v$database; 
DATABASE_ROLE    PROTECTION_MODE      PROTECTION_LEVEL     OPEN_MODE 
---------------- -------------------- -------------------- -------------------- 
PRIMARY          MAXIMUM PERFORMANCE  MAXIMUM PERFORMANCE  READ WRITE 
#standby 端查看，也是一样的。 
SQL> select database_role,protection_mode,protection_level,open_mode from v$database; 
DATABASE_ROLE    PROTECTION_MODE      PROTECTION_LEVEL     OPEN_MODE 
---------------- -------------------- -------------------- -------------------- 
PHYSICAL STANDBY MAXIMUM PERFORMANCE  MAXIMUM PERFORMANCE  MOUNTED 
查看DG的日志信息
SQL> select * from v$dataguard_status;
Open Read Only standby数据库并且开启实时日志应用
SQL> shutdown immediate 
ORA-01109: database not open 
Database dismounted. 
ORACLE instance shut down. 
SQL> startup 
ORACLE instance started. 
Total System Global Area 1188511744 bytes 
Fixed Size                  1364228 bytes 
Variable Size             754978556 bytes 
Database Buffers          419430400 bytes 
Redo Buffers               12738560 bytes 
Database mounted. 
Database opened. 
SQL> select database_role,protection_mode,protection_level,open_mode from v$database; 
DATABASE_ROLE    PROTECTION_MODE      PROTECTION_LEVEL     OPEN_MODE 
---------------- -------------------- -------------------- -------------------- 
PHYSICAL STANDBY MAXIMUM PERFORMANCE  MAXIMUM PERFORMANCE  READ ONLY 
SQL> select process,client_process,sequence#,status from v$managed_standby; 
PROCESS   CLIENT_P  SEQUENCE# STATUS 
--------- -------- ---------- ------------ 
ARCH      ARCH              0 CONNECTED 
ARCH      ARCH              0 CONNECTED 
ARCH      ARCH              0 CONNECTED 
ARCH      ARCH             26 CLOSING 
RFS       ARCH              0 IDLE 
RFS       UNKNOWN           0 IDLE 
RFS       LGWR             27 IDLE 
7 rows selected. 
SQL> recover managed standby database using current logfile disconnect from session; 
Media recovery complete. 
SQL> select process,client_process,sequence#,status from v$managed_standby; 
PROCESS   CLIENT_P  SEQUENCE# STATUS 
--------- -------- ---------- ------------ 
ARCH      ARCH              0 CONNECTED 
ARCH      ARCH              0 CONNECTED 
ARCH      ARCH              0 CONNECTED 
ARCH      ARCH             26 CLOSING 
RFS       ARCH              0 IDLE 
RFS       UNKNOWN           0 IDLE 
RFS       LGWR             27 IDLE 
MRP0      N/A              27 APPLYING_LOG 
8 rows selected. 
SQL> select process,client_process,sequence#,status from v$managed_standby;
PROCESS   CLIENT_P  SEQUENCE# STATUS
--------- -------- ---------- ------------
ARCH   ARCH         19 CLOSING
ARCH   ARCH         20 CLOSING
ARCH   ARCH          0 CONNECTED
ARCH   ARCH         21 CLOSING
MRP0   N/A          22 WAIT_FOR_LOG
RFS   ARCH          0 IDLE
RFS   UNKNOWN       0 IDLE
RFS   UNKNOWN       0 IDLE
RFS   LGWR         22 IDLE
9 rows selected.

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