ORA-16857: standby disconnected from redo source for longer than specified threshold

DGMGRL> show configuration

Configuration - usage

  Protection Mode: MaxPerformance
  Members:
  usage   - Primary database
    usagedr - Physical standby database
      Warning: ORA-16857: standby disconnected from redo source for longer than specified threshold

Fast-Start Failover: DISABLED

Configuration Status:
WARNING   (status updated 14 seconds ago)

DGMGRL> show database usage

Database - usage

  Role:               PRIMARY
  Intended State:     TRANSPORT-ON
  Instance(s):
    usage1
    usage2

Database Status:
SUCCESS

DGMGRL> show database usagedr

Database - usagedr

  Role:               PHYSICAL STANDBY
  Intended State:     APPLY-ON
  Transport Lag:      23 minutes 55 seconds (computed 2 seconds ago)
  Apply Lag:          23 minutes 56 seconds (computed 2 seconds ago)
  Average Apply Rate: 1.40 MByte/s
  Real Time Query:    OFF
  Instance(s):
    usagedr1 (apply instance)
    usagedr2

Database Status:
SUCCESS

DGMGRL>

Solution

Setting 'TransportDisconnectedThreshold' to 0 seconds will disable the alert else we can set the property to a higher value.