一套Oracle 19c的ADG集群要修改sys密码，由于之前遇见过11g上sys密码修改导致同步问题的情况，所以改之前特意查了下文档，发现其实12cR2开始，在主库修改密码就会自动同步到备库了，以下是一段官方文字描述，可以参考。
When password file is used for Redo Transport Authentication, the password of redo transport user should be same across primary and all its physical and snapshot standby databases. By default SYS user is used to authenticate redo transport sessions when password file is used.
Till 12cR1 Dataguard setup, if there is a change in password file of Primary database like Changes in password or Changes in admin privileges, then the password file needs to be copied from Primary database to standby database server and rename it according to standby database Instance name. If the password file of Primary and Standby databases are not same, then errors will be seen.
In 12cR2, the password file of standby database gets synchronized automatically when there is a change in Primary database password file. The password file change of Primary will be included in Redo and when the Redo is applied to standby, the synchronization happens in the background.
以下是验证过程。
主库密码文件：修改前
-rw-r----- 1 oracle oinstall 2048 Oct 11 18:21 orapwtsqldb
修改主库sys密码：
alter user sys identified by "EWRweRW#12#%";
主库密码文件：修改后
-rw-r----- 1 oracle oinstall 2048 Nov 2 10:16 orapwtsqldb
此时备库也跟着同步了密码文件：
-rw-r----- 1 oracle oinstall 2048 Oct 14 10:41 orapwtsqldb
修改后密码文件：
-rw-r----- 1 oracle oinstall 2048 Nov 2 10:16 orapwtsqldb
可见oracle还是用心的 :}