ORA-16649: possible failover to another database prevents this database from being opened
Cause: An attempt to open the primary database was made either after a failover occurred, or when it was likely to have occurred as the result of the primary being isolated from the fast-start failover target standby database and from the fast-start failover observer.
Action: Check if a failover did occur. If fast-start failover is enabled, and a failover did not occur, ensure that connectivity exists between the primary database and either the observer or the target standby database. Then, try opening the database again.
ORA-16649 是Oracle数据库中的错误信息，它表明可能发生了失败转移，从而阻止本数据库打开。
1. 确保可执行失败转移操作的客户端程序（例如Oracle Enterprise Manager或Oracle Data Guard）正确配置，database目录可以正常访问；
2. 使用alter system set enable_fal_server = true 命令开启fal_server服务以接收失败转移请求；
3. 使用alter system register standby database语句注册失败的数据库，以确保可正常接收失败转移的所有消息；
4. 确保修改数据库状态并解决失败转移操作后，重新打开本数据库即可。