The standby database use real time apply by default in oracle rdbms version 12c, but the v$dataguard_stats shows minutes or hours of lagging on transport and apply, v$managed_standby shows the MRP0 block#=0, means it's not doing the real time apply. The standby logs are all active and not being archived. The root cause of this problem is the archive_dest_1 (or 2) specified "valid_for=(all_roles, online_logfile), it should be "all_logfiles". After fixing this parameter and switch logfile, real time apply is working ok, archive logs are being generated correctly, only one standby logs status remain "active".
