Since the parameters

LOG_ARCHIVE_DEST & STANDBY_ARCHIVE_DEST are of dynamic parameters in 8.1.7, you can reset them as follows

Login as sys@sid as sysdba
Code:
     ALTER SYSTEM SET LOG_ARCHIVE_DEST_2 = '';
     ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2 = DISABLE;
     ALTER SYSTEM SET STANDBY_ARCHIVE_DEST = '';

     COMMIT;
Hopefully this will fix

Sam