12cR2 RAC+RAC+ADG ORA-16854

   近期在某銀行生產搭建了一套RAC+RAC+ADG+BROKER的生產系統，遇到了不少坑，再此做一個記錄。大家有疑問，可以給我留言，一起討論學習。

1、環境描述
Oralce 12cR2 RAC+RAC ADG broker

2、類似現象
DGMGRL> show configuration verbose

Configuration - FSF

Protection Mode: MaxAvailability
Members:
test_a - Primary database
standby_c - Physical standby database
standby_b - Physical standby database
Warning: ORA-16854: apply lag could not be determined
##告警ORA-16854 無法確認應用延遲，告警現象和我遇到的是一模一樣的。

3、解決方法
MOS 官方提供了兩個方法，具體情況還需要進一步分析
1)有可能是BUG
Workaround: set the ApplyLagThreshold=0 but this means you will not receive notifications of apply lag in Broker for the specified Standby database:

                 dgmgrl> edit database <standby db_unique_name> set property ApplyLagThreshold=0;

Please download and apply existing fix for BUG 28803345 or open SR and request backport of BUG 28803345 to resolve the issue.
2)重建控制文件
To solve this issue, recreate the standby controlfile.

Here steps for how to recreated the standby controlfile:

Steps to recreate a Physical Standby Controlfile (Doc ID 459411.1)

Please note in few cases apply lag in v$dataguard_stats was null in the database and Clearing ORLs in standby helped resolve the NULL value issue.

4、開SR
有條件或者服務的朋友可以開一個SR，明確一下問題。