oracle 12c data guard如何使用 sqlplus 主备切换

小编给大家分享一下oracle 12c data guard如何使用 sqlplus 主备切换，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！

第一，切换之前的检查。

确认备库已经准备好切换

确认备库与主库是同步的并且日志切换正常。

SQL>alter database switchover to <target standby db_unique_name> verify;

以上命令会验证如下信息：

a. 验证数据库的版本至少为 12.1。

b. 主库 REDO 传输正常。

c. 备库 MRP 进程正常运行并且与主库同步，否则会在 SQLPROMPT 和 alert 中都报如下错误：

列如：

SQL>alter database switchover to chicaGo verify;

ORA-16470: Redo Apply is not running on switchover target

------Primary alert log------

    SQL>alter database switchover to chicago verify;

    ORA-16470 signaled during: alter database switchover to chicago verify...

在目标备库上检查 ORL 的状态

如果是脏的那么会报出如下信息：

SQL> alter database switchover to chicago verify;

ERROR at line 1:

ORA-16475: succeeded with warnings, check alert log for more details

-----Primary Alert log-----------

SWITCHOVER VERIFY WARNING: switchover target has dirty online redo logfiles that require clearing.

It takes time to clear online redo logfiles. This may slow down switchover process.

需要做什么呢？

确认 log_file_name_convert 参数在目标备库被正确设置：

SQL>show parameter log_file_name_convert;

注意：如果没有设置，请设置。例如，如果路径结构只有 db_uniquq_name 发生了改变：

主库的日志在： /oradata/boston/<>

备库的日志在： /oradata/chicago/logfiles>

这样设置参数：

alter system set LOG_FILE_NAME_CONVERT=’boston’,’chicago’ scope=spfile;  

注意：重启备库并且启动 MRP。当重启备库并且启动 MRP，将清除所有备库的 log_file_name_convert 参数设置的日志。

如果备库是与主库同步的，将得到如下的信息：

SQL> alter database switchover to chicago verify;

Database altered.

--------- Primary Alert log -------

SWITCHOVER VERIFY: Send VERIFY request to switchover target CHICAGO

SWITCHOVER VERIFY COMPLETE

Completed: alter database switchover to chicago verify

确认主库和备库的临时数据文件匹配

临时数据文件在创建备库之后，不会同时创建临时数据文件，用如下的命令查询临时数据文件，并且在备库进行创建。

SQL> col name for a45

SQL>  select ts#,name,ts#,status  from v$tempfile;

注意：对于多个备库的环境，确保每个备库与主库同步。

Check if log_arcHive_Dest(remote redo transport) set on Standby side

SWITCHOVER VERIFY command returns ORA-16475 when log_archive_dest_n is not set on Standby as follows.

SQL> ALTER DATABASE SWITCHOVER TO S1202 VERIFY;
ALTER DATABASE SWITCHOVER TO S1202 VERIFY
*
ERROR at line 1:
ORA-16475: succeeded with warnings, check alert log for more details

In alert.log, following messages appear.

SWITCHOVER VERIFY: Send VERIFY request to switchover target S1202
SWITCHOVER VERIFY COMPLETE
SWITCHOVER VERIFY WARNING: switchover target has no standby database definedin LOG_ARCHIVE_DEST_n parameter. If the switchover target is converted to
a primary database, the new primary database will not be protected.ORA-16475 signalled during: ALTER DATABASE SWITCHOVER TO S1202 VERIFY...

What to do?  set log_archive_dest_state_n on Standby.

如果 v$database 的 switchover_status 的值为 UNRESOLVABLE GAP（RAC 或者非 RAC）

1. 检查是否有些关闭的线程存在并且 disable

SQL>SELECT thread#, instance, status FROM v$thread;

Disable 线程使用：

SQL> ALTER DATABASE DISABLE THREAD <n>;

2. 检查是否有 log_archive_destination 指向不合法的目录

SQL> select status,DEST_ID,TYPE,ERROR,GAP_STATUS,SYNCHRONIZED,SYNCHRONIZATION_STATUS,RECOVERY_MODE from V$ARCHIVE_DEST_STATUS where STatus <> 'INACTIVE';
SQL>show parameter log_Archive_dest

第二，切换角色

在主库和备库同时开启 trace，用于发生问题时候的诊断。

SQL>alter system set log_archive_trace=8191 sid=’*’;

监视各个实例的 alert log（可选）

@primary and standby,

SQL>show parameter background_dump_dest

$tail -600f background_dump_dest/alert*

* 注意: 在 RAC 环境不需要关闭其他的实例，执行 Switchover 的命令会关闭所有的实例。

切换备库角色为主库

主库 - Boston,

SQL>alter database switchover to chicago;

Database altered.

以下是主库（BOSTON）和备库（CHICAGO）的 alert 输出：

--------------Primary Alert log "alert_boston.log"--------------

Fri Aug 23 11:05:23 2013

ALTER SYSTEM SET log_archive_trace=8191 SCOPE=BOTH;

 alter database switchover to chicago

Fri Aug 23 11:05:43 2013

Starting switchover [Process ID: 3340]

Fri Aug 23 11:05:43 2013

ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY [Process Id: 3340] (boston)

.

Fri Aug 23 11:05:44 2013

Active, synchronized Physical Standby switchover target has been identified

Preventing updates and queries at the Primary

Generating and shipping final logs to target standby

Switchover End-Of-Redo Log thread 1 sequence 11 has been fixed   <--------- 序列号 11 是日志的终止序号

Switchover: Primary highest seen SCN set to 0x0.0x229306

ARCH: Noswitch archival of thread 1, sequence 11

.

Switchover: Primary controlfile converted to standby controlfile succesfully.

Switchover: Complete - Database shutdown required

Sending request (convert to primary database) to switchover target CHICAGO

OCISessionBegin with PassWordVerifier succeeded

Switchover complete. Database shutdown required

USER (ospid: 3340): terminating the instance

Fri Aug 23 11:05:51 2013

Instance terminated by USER, pid = 3340

Completed:  alter database switchover to chicago

-------------------alert log "alert_chicago.log"------------------

Fri Aug 23 11:05:47 2013

SWITCHOVER: received request 'ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY' from primary database.

Fri Aug 23 11:05:47 2013

ALTER DATABASE SWITCHOVER TO PRIMARY (chicago)

Maximum wait for role transition is 15 minutes.

.

Standby became primary SCN: 2265860

Switchover: Complete - Database mounted as primary

SWITCHOVER: completed request from primary database.

注意：备库一端只等待15分钟，实现备库与主库的同步。

打开新的主数据库

SQL>alter database open;

重启新的备库

SQL>shut abort

SQL>startup

SQL>alter database recover managed standby database disconnect;

第三，切换后的后续步骤

关闭 trace

SQL>  alter system set log_archive_trace=0;

System altered.

确认新的主库已经正常传输日志到备库，并且备库能正常应用。

在主库侧执行

SQL>alter system switch logfile;

SQL>select dest_id,error,status from v$archive_dest where dest_id=<your remote log_archive_dest_<n>>;

SQL>select max(sequence#),thread# from v$log_history group by thread#;

如果备库端对应 log_archive_dest_2

SQL>select max(sequence#)  from v$archived_log where applied='YES' and 
dest_id=2;

在备库侧：

SQL>select thread#,sequence#,process,status from gv$managed_standby;

SQL>select max(sequence#),thread# from v$archived_log group by thread#;

注意：在 12.2 中使用 v$dataguard_process 替代 v$managed_standby

SQL> select name,role,instance,thread#,sequence#,action from gv$dataguard_process;

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