DBID on Oracle Data Guard

Dear Oracle Experts,

After my physical standby database was set up, I changed DBID on the standby DB.

Old DBID was 13477809. It was same as my primary DBID.

New DBID is 30359872.

Unfortunately, archive log files stopped to send on standby DB.

I got an error msg on the two servers,

ORA-16012: Archive log standby database identifier mismatch

On standby DB

SQL> select group#, dbid, status from v$standby_log

GROUP# DBID STATUS
-- --- --
4 13477809         ACTIVE
6 UNASSIGNED UNASSIGNED

5 UNASSIGNED UNASSIGNED

7 UNASSIGNED UNASSIGNED

My questions, 

1. How can I fix up the error?

2. Was that right to change DBID on standby DB?