1. DCS periods are different than MRV periods and do not take cargo operation into account. Arrival and Departure reports need to be reported every time the vessel drops Anchor, regardless cargo operation. Station type is used to clarify to users (office and crew) the type of the stoppage. 
2. Even in MRV regulation, where cargo operation matters, Fleet Manager does not split the periods only regarding Arrival and Departure Reports, but also checks whether cargo has changed. Thus, a vessel may report Arrival and Departure, and if there was no cargo operation the period will not change. 
3.Vessels must report Arrival and Departures according to whether they are in port/anchorage or not, regardless cargo operation. 

4. Kindly note how Time at sea is calculated for MRV purposes  
Time at sea is calculated for “at sea” periods and is set to “0” for “in port” periods. 
An "at sea" period starts after a Departure (the last Departure before a reported COSP)  report and may include port stays if there is no cargo operation in a specific port. 
The “at sea” period will be complete and the next “in port”  period will begin when the vessel reaches a port where cargo operation takes place. 
For example, consider a case where, period ## is an “at sea” period. 
It starts after Departure (the last reported Departure before COSP) and though the vessel reaches a port, there is no cargo operation, so this time is considered as “time at sea” and is calculated. 
Period ## is completed with an Arrival report  if  during the next port period cargo operation takes place. 

5. for DCS periods there is no rule for cargo operation - every in-port period is excluded  from "time at sea".
Time at sea is calculated for “at sea” periods and is set to “0” for “in port” periods. 
An "at sea" period starts after a Departure (the last Departure before a reported COSP) . 
The “at sea” period will be complete and the next “in port”  period will begin when the vessel reaches a port and reports Arrival. 

For example, consider a case where, period ## is an “at sea” period. It starts after a Departure  (that is followed by delay reports and finally a COSP). 
Period ## is completed with an Arrival report  when the vessel drops Anchor or gets to Berth (station type clarifies anchor/berth)