SWITCHOVER主库出现LOG SWITCH GAP和RESOLVABLE GAP解决一例(三)
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READ WRITE PHYSICAL STANDBY RECOVERY NEEDED
SQL> shutdown abort
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 413372416 bytes
Fixed Size 2228904 bytes
Variable Size 331353432 bytes
Database Buffers 75497472 bytes
Redo Buffers 4292608 bytes
Database mounted.
原备库：
SQL> select open_mode,database_role,switchover_status from v$database;
OPEN_MODE DATABASE_ROLE SWITCHOVER_STATUS
-------------------- ---------------- --------------------
READ ONLY WITH APPLY PHYSICAL STANDBY TO PRIMARY
SQL> alter database commit to switchover to primary;
Database altered.
SQL> alter database open;
Database altered.
SQL> select open_mode,database_role,switchover_status from v$database;
OPEN_MODE DATABASE_ROLE SWITCHOVER_STATUS
-------------------- ---------------- --------------------
READ WRITE PRIMARY TO STANDBY
原主库(新备库)：
SQL> alter database recover managed standby database using current logfile disconnect from session;
Database altered.
SQL> select open_mode,database_role,switchover_status from v$database;
OPEN_MODE DATABASE_ROLE SWITCHOVER_STATUS
-------------------- ---------------- --------------------
MOUNTED PHYSICAL STANDBY RECOVERY NEEDED
此时刚转换好的新备库SWITCHOVER状态是RECOVERY NEEDED，这是正常的，主库切几次日志以后就会变成NOT ALLOWED状态了，另外这个时候由于是REDO APPLY模式，虽然是11g，但也是无法直接OPEN的，如果要OPEN，必须先停止REDO APPLY：
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-10456: cannot open standby database; media recovery session may be in progress
SQL> alter database recover managed standby database cancel;
Database altered.
SQL> alter database open;
Database altered.
由于11g的ACTIVE DG功能(需要LISENCE，否则属于非法使用)，所以即便在OPEN状态下，依然能够REDO APPLY：
SQL> alter database recover managed standby database disconnect;
Database altered.
SQL> select open_mode,database_role,switchover_status from v$database;
OPEN_MODE DATABASE_ROLE SWITCHOVER_STATUS
-------------------- ---------------- --------------------
READ ONLY WITH APPLY PHYSICAL STANDBY NOT ALLOWED
至此，整个SWITCHOVER就做完了，SWITCHOVER是不会丢失数据的(不同于FAILOVER)，如果FAILOVER能做到没有GAP，也可以不丢数据，并且正常使用SWITCHOVER切换