Oracle DG 主备切换

谷遇到这种问题，一般是主库异常宕机，一时半会没有办法恢复，且没有有效的监控配置，来将备库自动提升为主库。否则，就是显得蛋疼。
在maximum protection和maximum availability两种模式

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 //切换主库带最大性能模式
         SQL> ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE;
 //切换主库带最大可用模式
         SQL> ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE AVALIABILITY;

在虚拟机环境下模式主库宕机，主备手动切换的操作如下：
1：主库宕机，所以先在备库操作
    查看归档日志文件是否已经完全应用，且没有GAP发生
    

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 SQL> select status,sequence#,thread# from v$managed_standby; STATUS          SEQUENCE#    THREAD# ------------ ---------- ---------- CONNECTED          0      0 CLOSING          80      1 CONNECTED          0      0 CONNECTED          0      0
 SQL> select sequence#,applied from v$archived_log;

  SEQUENCE# APPLIED
 ---------- ---------
     64 YES
     65 YES
     66 YES
     67 YES
     68 YES
     69 YES
     70 YES
     71 YES
     72 YES
     73 YES
     74 YES

  SEQUENCE# APPLIED
 ---------- ---------
     75 YES
     76 YES
     77 YES
     79 YES
     80 YES
     78 YES

 17 rows selected.
 SQL> SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP; no rows selected
 #如果查出又值，为保证数据完整性，则需要从主库拷贝到备库，并且注册。例如
 SQL> ALTER DATABASE REGISTER or replace PHYSICAL LOGFILE 'filespec1';

以上应用日志全是 YES 状态则表明传过来的日志已经全部应用完成，且不存在GAP。

-------可选----然后停止 standby 自动管理，添加在线日志文件组（成员）、删除无效日志组（成员）

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 SQL> show parameter standby

 NAME                 TYPE     VALUE
 ------------------------------------ ----------- ------------------------------
 standby_archive_dest         string     ?/dbs/arch
 standby_file_management      string     AUTO
 SQL> alter system set standby_file_management=MANUAL;

 System altered.
 SQL> select * from v$logfile;
 GROUP# STATUS  TYPE    MEMBER                          IS_ ---------- ------- ------- -------------------------------------------------- ---      1       ONLINE  /data/oracle/orcl/redo01.dbf               NO      2       ONLINE  /data/oracle/orcl/redo02.dbf               NO      3       ONLINE  /data/oracle/orcl/redo03.dbf               NO      4       STANDBY /data/oracle/orcl/standby01.log              NO
 //日志组1、2、3是无效的，所以需要添加日志组文件（组）
 SQL> alter database add logfile member '/data/oracle/orcl/redo04.dbf' to group 1; Database altered. SQL> alter database add logfile member '/data/oracle/orcl/redo05.dbf' to group 2; Database altered. SQL> alter database add logfile member '/data/oracle/orcl/redo06.dbf' to group 3; Database altered.
 SQL> alter database add logfile member '/data/oracle/orcl/redo06.dbf' to group 3; Database altered.
 ----可选添加

       SQL> alter database add standby logfile 5 ('/data/oracle/orcl/standby06.dbf',/data/oracle/orcl/standby06_b.dbf')  size 100m;

       Database altered.

 SQL> select * from v$logfile;     GROUP# STATUS  TYPE    MEMBER                          IS_ ---------- ------- ------- -------------------------------------------------- ---      1       ONLINE  /data/oracle/orcl/redo01.dbf               NO      2       ONLINE  /data/oracle/orcl/redo02.dbf               NO      3       ONLINE  /data/oracle/orcl/redo03.dbf               NO      4       STANDBY /data/oracle/orcl/standby01.log              NO      1 INVALID ONLINE  /data/oracle/orcl/redo04.dbf               NO      2 INVALID ONLINE  /data/oracle/orcl/redo05.dbf               NO      3 INVALID ONLINE  /data/oracle/orcl/redo06.dbf               NO 7 rows selected.

备库切换：

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 SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH FORCE;

 Database altered.

 SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;

 Database altered.

 SQL> shutdown immediate
 ORA-01109: database not open


 Database dismounted.
 ORACLE instance shut down.
 SQL> startup ORACLE instance started. Total System Global Area  521936896 bytes Fixed Size            2214936 bytes Variable Size          314573800 bytes Database Buffers      201326592 bytes Redo Buffers            3821568 bytes Database mounted. Database opened.
 SQL> select open_mode from v$database; OPEN_MODE -------------------- READ WRITE

原先的主库需要重做

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