Oracle 11g Active Dataguard Switchover实验 - 数据库编程

相关参考:

1、环境介绍

SQL> select * from v$version;

BANNER

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

Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - Production

PL/SQL Release 11.2.0.4.0 - Production

CORE 11.2.0.4.0 Production

Primary数据库unique名称为ora11g。

SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;

NAME LOG_MODE OPEN_MODE DATABASE_ROLE SWITCHOVER_STATUS DB_UNIQUE_NAME

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

ORA11G ARCHIVELOG READ WRITE PRIMARY SESSIONS ACTIVE ora11g

Standby数据库名称为ora11gsy，此时开启实时数据同步应用。

SQL> alter database recover managed standby database using current logfile disconnect from session;

Database altered

SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;

注意：此时standby的open mode为Read only with apply，这个是11g Active Data Guard的特性。传统DG在进行Apply的过程中，是处在mount状态的，不支持实时数据只读操作。11g支持在apply中打开数据库到只读状态。

2、Switchover过程中Primary主库操作

进行Switchover的过程分为三个步骤，一个是在Primary上停止工作，切换到Standby状态，第二个是在选择一个Standby实例，切换角色到Primary状态，最后是将其他Standby的Apply过程启动。

注意在上面我们查看Primary数据库ora11g的v$database视图，其中switchover_status取值是我们需要关注的，如果取值为session active或者to standby，我们是可以进行切换的。如果其他值，说明配置的log传输机制存在问题，需要解决调整。

--在ora11g上

SQL> alter database commit to switchover to physical standby with session shutdown;

Database altered

注意：如果swtichover_status状态为session active，就需要在命令中加入with session shutdown子句。执行后，我们发现Primary ora11g已经关闭。

SQL> select status from v$instance;

select status from v$instance

ERROR at line 1:

ORA-03135: connection lost contact

Process ID: 2357

Session ID: 1 Serial number: 5

SQL> exit

Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

--实例进程消失

[oracle@SimpleLinux trace]$ ps -ef | grep pmon

oracle 2107 1 0 15:35 00:00:01 ora_pmon_ora11gsy

oracle 2473 1848 1 16:03 pts/1 00:00:00 grep pmon

此时，alert log中也记录了实例停止的情况。

ALTER DATABASE ADD STANDBY LOGFILE 'srl1.f' SIZE 52428800;

ALTER DATABASE ADD STANDBY LOGFILE 'srl2.f' SIZE 52428800;

ALTER DATABASE ADD STANDBY LOGFILE 'srl3.f' SIZE 52428800;

ALTER DATABASE ADD STANDBY LOGFILE 'srl4.f' SIZE 52428800;

Archivelog for thread 1 sequence 19 required for standby recovery

Switchover: Primary controlfile converted to standby controlfile succesfully.

Switchover: Complete - Database shutdown required

USER (ospid: 2365): terminating the instance

Instance terminated by USER, pid = 2365

Completed: alter database commit to switchover to physical standby with session shutdown

Shutting down instance (abort)

License high water mark = 6

Sun Apr 20 16:02:11 2014

Instance shutdown complete

在这个过程中，为了确保数据无损失，Primary一定将所有的日志信息传递到Standby上。此时，可以启动Primary，到mount standby状态。

[oracle@SimpleLinux trace]$ sqlplus /nolog

SQL*Plus: Release 11.2.0.4.0 Production on Sun Apr 20 16:06:47 2014

Oracle 11g Active Dataguard Switchover实验(一)