Troubleshooting of arch error in DG

SQL> select process, status from v $ managed_standby;

PROCESS STATUS
---------------------
ARCH CONNECTED
ARCH ERROR
RFS IDLE
RFS IDLE

Check parameter and find log_archive_dest_state_2 sets ENABLE. Because no switch over is performed, this parameter is useless for my DG.

So:

Alter system set log_archive_dest_state_2 = 'delete' scope = both;

Re-query:

SQL> select process, status from v $ managed_standby;

PROCESS STATUS
---------------------
ARCH CONNECTED
ARCH ERROR
MRP0 WAIT_FOR_LOG
RFS IDLE
RFS IDLE

No effect.

View parameters:

Log_archive_max_processes integer 2

There is actually only one valid ARCH process for me, so:

Alter system set log_archive_max_processes = 1 scope = 1;

SQL> select process, status from v $ managed_standby;

PROCESS STATUS
---------------------
ARCH CONNECTED
RFS IDLE
RFS IDLE
MRP0 WAIT_FOR_LOG

Return:

Alter system set log_archive_max_processes = 2 scope = 2;

SQL> select process, status from v $ managed_standby;

PROCESS STATUS
---------------------
ARCH CONNECTED
ARCH CONNECTED
RFS IDLE
RFS IDLE
MRP0 WAIT_FOR_LOG

Solve the problem.