Oracle DataGuard 主備切換switchover

環境：

OS：rhel63_64bit

DB: Oracle10gR2

主備切換 切換的順序： 先從主庫到備用，再從備庫到主庫
Switchover Switchover：
無損轉換，通常是使用者手動觸發或者有計劃的讓其自動觸發，比如硬體升級啦，軟體升級啦之類的。
通常它給你帶來的工作量非常小並且都是可預計的。其執行分兩個階段，第一步，primary 資料庫轉換為standby 角色，第二步，standby 資料庫(之一)轉換為 primary 角色，primary 和 standby 只是簡單的角色互換，這也印證了我們前面關於角色轉換是 primary/standby 互動的猜測。
Failover Failover：
不可預知原因導致 primary 資料庫故障並且短期內不能恢複就需要 failover。如果是這種切換那你就要小心點了，有可能只是虛驚一場，甚至連你可能損失的腦細胞的數量都能預估，但如果運氣不好又沒有完備的備份恢複策略而且 primary 資料並非處於最大資料保護或最高可用性模式地話

SWITCHOVER_STATUSVARCHAR2(18)Indicates whether switchover is allowed:
■NOT ALLOWED - Either this is a standby database and the primary
database has not been switched first or this is a primary database
and there are no standby databases.
■SESSIONS ACTIVE - Indicates that there are active SQL sessions
attached to the primary or standby database that need to be
disconnected before the switchover operation is permitted. Query
theV$SESSIONviewtoidentifythespecificprocessesthatneedto
be terminated.
■SWITCHOVER PENDING - This is a standby database and the
primary database switchover request has been received but not
processed.
■SWITCHOVER LATENT - The switchover was in pending mode,
but did not complete and went back to the primary database.
■TOPRIMARY-Thisisastandbydatabaseandisallowedtoswitch
over to a primary database.
■TOSTANDBY-Thisisaprimarydatabaseandisallowedtoswitch
over to a standby database.
■RECOVERY NEEDED - This is a standby database that has not
received the switchover request.
主庫操作
SQL>  select process,pid,status,client_process from v$managed_standby;

PROCESS          PID STATUS      CLIENT_P
--------- ---------- ------------ --------
ARCH            7913 CONNECTED    ARCH
ARCH            7915 CONNECTED    ARCH
ARCH            7917 CLOSING      ARCH
ARCH            7919 CONNECTED    ARCH
ARCH            7921 CONNECTED    ARCH
ARCH            7923 CONNECTED    ARCH
ARCH            7925 CONNECTED    ARCH
ARCH            7927 CONNECTED    ARCH
ARCH            7929 CONNECTED    ARCH
ARCH            7931 CONNECTED    ARCH
LGWR            7893 WRITING      LGWR

11 rows selected.

SQL>  select DATABASE_ROLE,switchover_status from v$database;

DATABASE_ROLE    SWITCHOVER_STATUS
---------------- --------------------
PRIMARY          SESSIONS ACTIVE

SQL>
sys@ORA>  SELECT COUNT(*) FROM V$SESSION WHERE USERNAME IS NOT NULL;

  COUNT(*)
----------
        1
SQL> startup force
ORACLE instance started.

Total System Global Area  213909504 bytes
Fixed Size                  2095152 bytes
Variable Size              88082384 bytes
Database Buffers          117440512 bytes
Redo Buffers                6291456 bytes
Database mounted.
Database opened.
SQL>  select DATABASE_ROLE,switchover_status from v$database;

DATABASE_ROLE    SWITCHOVER_STATUS
---------------- --------------------
PRIMARY          SESSIONS ACTIVE

SQL>  SELECT COUNT(*) FROM V$SESSION WHERE USERNAME IS NOT NULL;

  COUNT(*)
----------
        1
沒有其他的會話，直接切換
SQL> select sequence#,applied from dba_logstdby_log;

no rows selected

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY WITH SESSION SHUTDOWN;

Database altered.
SQL> alter database commit to switchover to standby;

Database altered.

SQL>  select instance_name,status from v$instance;

INSTANCE_NAME    STATUS
---------------- ------------
ora          STARTED
SQL> shutdown immediate
ORA-01507: database not mounted

ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.

Total System Global Area  213909504 bytes
Fixed Size                  2095152 bytes
Variable Size              92276688 bytes
Database Buffers          113246208 bytes
Redo Buffers                6291456 bytes
Database mounted.
sys@ORA>  select DATABASE_ROLE,switchover_status from v$database;

DATABASE_ROLE    SWITCHOVER_STATUS
---------------- --------------------
PHYSICAL STANDBY TO PRIMARY

SQL>  select process,pid,status,client_process from v$managed_standby;

PROCESS          PID STATUS      CLIENT_P
--------- ---------- ------------ --------
ARCH            8126 CONNECTED    ARCH
ARCH            8128 CONNECTED    ARCH
ARCH            8130 CONNECTED    ARCH
ARCH            8132 CONNECTED    ARCH
ARCH            8134 CONNECTED    ARCH
ARCH            8136 CONNECTED    ARCH
ARCH            8138 CONNECTED    ARCH
ARCH            8140 CONNECTED    ARCH
ARCH            8142 CONNECTED    ARCH
ARCH            8144 CONNECTED    ARCH

10 rows selected.

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