客户数据库宕掉了，连接过去一看
可以正常到mount状态，然后alter database open，观察日志里面提示：
ORA-19809: limit exceeded for recovery files
Cause: The limit for recovery files specified by the DB_RECOVERY_FILE_DEST_SIZE was exceeded.
查询官方对错误的处理方式如下：
http://docs.oracle.com/cd/E16655_01/server.121/e26079/e19500.htm
ORA-19809: limit exceeded for recovery files
Cause:The limit for recovery files specified by the DB_RECOVERY_FILE_DEST_SIZE was exceeded.
Action:There are five possible solutions:
1) Take frequent backup of recovery area using RMAN.
2) Consider changing RMAN retention policy.
3) Consider changing RMAN archived log deletion policy.
4) Add disk space and increase DB_RECOVERY_FILE_DEST_SIZE.
5) Delete files from recovery area using RMAN.
于是做如下操作：
crosscheck archivelog all;
直接删除7天之前的归档日志，腾出空间来
delete noprompt archivelog until time 'sysdate - 7';
现在sqlplus / as sysdba过去，正常启动数据库
SQL> select status from v$instance;
STATUS
------------
MOUNTED
SQL> alter database open;
SQL> select status from v$instance;
STATUS
------------
OPEN
后续处理，防止该问题频繁发生：
RMAN> CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 7 DAYS;
RMAN> CONFIGURE CONTROLFILE AUTOBACKUP ON;
SQL> alter system set db_recovery_file_dest_size=10G scope=both;
SQL> alter system set log_archive_dest_1='location=/opt/oracle/oradata/archive_log' scope=both;
现在切换日志alter system archive log current;可以通过select name from v$archived_log;查看，看归档已经到了新路径，也可去select name from v$archived_log;下检查。
分析：导致该问题主要由于归档日志在快速恢复区下，当快速恢复区被充满的时候，则无法进行归档，所以导致数据库宕机，处理方式即
（1）改变rman的策略，从而进行定期清理归档日志。
（2）修改归档路径，从而不受快速恢复区的影响
（3）修改db_recovery_file_dest_size大小
