Warning: ORA-16854: Apply Lag Could Not Be Determined

Cause:

Dataguard replication was functioning properly and there were no failures in any of the alert logs, a warning ORA-16854: apply lag could not be determined in dgmgrl show configuration command was displayed.  Tried to validate database command, but the warning remained.

Solution:

Restart the MRP on the standby database after cancelling the recovery.

SQL> alter database recover managed standby database cancel;
 Database altered.
SQL> alter database recover managed standby database using current logfile disconnect from session;
 Database altered.

DGMGRL> show configuration;
 Configuration - DG_Broker_DR
 Protection Mode: MaxPerformance
Members:
primary - Primary database
standby - Physical standby database
 Fast-Start Failover: DISABLED
 Configuration Status:
SUCCESS (status updated 5 seconds ago)