RMAN-08120:WARNING: archived log not deleted, not yet applied by standby

在12C版本数据库部署自动清理归档脚本，查看删除日志报错，在11g中未出现过此警告，感觉是12C的新特性导致。

RMAN-08120:WARNING: archived log not deleted, not yet applied by standby

这个问题，是因为在12.1.0.2中，删除归档日志的默认行为发生了变化。原来在11g中不考虑defer的路径，在12.1.0.2时如果有defer的路径，则会报错日志没有applied，即使这些日志实际上已经被applied了。

This behavior has changed and is related to:

Bug 16082541 RMAN DELETES ARCHIVELOGS WHICH HAVE NOT BEEN APPLIED TO A DEFERRED STANDBY
which was fixed in 12.1.0.2, ( but has changed behaviour in handling of deleting logs)

Changed behaviour:
-> Destinations that are marked DEFERRED (and valid_now=’UNKNOWN’) are considered in in 12.1.0.2 before deleting logs.

排查过程：

检查log_archive_dest_status_n参数是否存在为defer

处理方法：

1. 不改log_archive_dest_state_n，设置log_archive_dest_n=''
2. 不取消log_archive_dest_n=''，修改log_archive_dest_state_n为enable  --确认有效
3. alter system set "_deferred_log_dest_is_valid"=false
4. archivelog deletion policy从applied on all standby改成applied on standby