> select open_mode,switchover_status,database_role from v$database;
OPEN_MODE SWITCHOVER_STATUS DATABASE_ROLE
-------------------- -------------------- ----------------
READ ONLY WITH APPLY NOT ALLOWED PHYSICAL STANDBY
SQL> select max(sequence#) from v$archived_log;
MAX(SEQUENCE#)
--------------
153
dg2：
SQL> select open_mode,switchover_status,database_role from v$database;
OPEN_MODE SWITCHOVER_STATUS DATABASE_ROLE
-------------------- -------------------- ----------------
READ WRITE TO STANDBY PRIMARY