日誌不得應用情況切換備庫為主庫

備庫執行如下：
alter database recover managed standby database disconnect from session;
alter database commit to switchover to primary

日誌反應如下：
Maximum wait for role transition is 15 minutes.
2016-09-07 12:57:20.653000 +08:00
Switchover: Media recovery is still active
Database not available for switchover
  End-Of-REDO archived log file has not been recovered
Database not available for switchover
  End-Of-REDO archived log file has not been recovered
2016-09-07 12:57:22.681000 +08:00
Database not available for switchover
  End-Of-REDO archived log file has not been recovered
Database not available for switchover
  End-Of-REDO archived log file has not been recovered
 
 
下面將STANDBY資料庫切換為PRIMARY資料庫：
  ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH;
    或
  ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH FORCE;
 
   SELECT DATABASE_ROLE FROM V$DATABASE;
　　DATABASE_ROLE
　　----------------
　　PHYSICAL STANDBY

　 ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;


這樣備庫可切換成primary 了