CP-SAT algorithm (The CP-SAT Solver is technologically superior to the original CP solver and should be preferred in almost all situations). 

This option applies to OR-tools, maximize pairing coverage, maximize reference activity coverage, and any fairness. This mean that each process will take around five minutes. If you have several Fairness Objectives (station fairness), it will take five minutes for each step. If the process time is too low, it might result an error. 

Reference activity to be used for Days Off. Day off fill in is mandatory for legality purposes.

Select the Rank you want to cover. It is only possible to run with one rank at a time. The crew select used in Auto rostering must correspond to this selection. Low Rank is currently not supported. 

If you have crew in the previous period without assigned Days OFF, and you have a constraint saying 4 days off in 14 days, this will make the Optimizer stop. To avoid this, you should use this option.

This option tries to distribute down ranked crew evenly.

It is possible to take the history days into account. Enter the number of days back that shall be calculated, and the total allowed number of down ranked legs in the loaded and historical period.

Needed if you use Legality Rules. This parameter also check for Base changes in the period. The parameter will be added as per default when you create a new template.

Note: Some max. period rules are not checked.

This is a rolling backwards parameter. This means that if you want 4 days OFF in 28 days, the Solver will look 28 days back for 4 days off, then assign 4 DO in the next 28 days.

It can happen that the DO are clustered, that has to be handled.

Note: The loaded crew must have assigned the corresponding number of Days OFF in the previous period; otherwise, you will get an error telling that crew xxx doesn't have the required DO.

This parameter refers to EASA ORO.FTL.235(d).

The minimum recurrent extended recovery rest period shall be 36 hours, including 2 local nights, and in any case the time between the end of one recurrent extended recovery rest period and the start of the next extended recovery rest period shall not be more than 168 hours. The recurrent extended recovery rest period shall be increased to 2 local days twice every month.

This parameter only works together with "At least x days off in y days".

The idea with the parameter is to spread the DO over the month. You will probably find that option 2 gives the best result.

1. You can use the “Max x DO in y days” constraint, but make sure that it is not conflicting with the “Min x days off in y days”. For example, if you use “Max 1 DO in 5 days”, then the “Min x DO in 28 days” need to have a parameter x that is 5 or lower. Since “Max 1 DO in 5 days” => “Max 6 DO in 30 days”.
   
   
2. You could also try to do it the other way around (if that makes practical sense). That is, to set “Max 10 DO in 28 days” and “Min 1 DO in 5 days”. This should give you at most 10 do in 20 days, but it should spread them out over the period, since it is not allowed to have any sub-period of 5 days without a DO.

Format: 18:00, 23:59, 06:00, 12:00

Pairings in the Late span are not allowed to be followed by a flight in the Early span.

Format: 3,18:00, 23:59, 06:00, 12:00

This parameter control how many late/early pairings you can have in a row.

This calculates Duty. Make sure you enter a realistic value.

E.g. if the max. duty is 100 per month, you shouldn't enter 60,7.

This function will assign min and max days off in the loaded period.

Compared to the "At least x days off in y days", this function will not look back into the previous period. The two functions shall not be used together.

You can create Reference Activity pairings, and let this parameter control the number of Reference activities in a period.

Syntax: "Ref act shortcode",min,max,days.

E.g. SBY,1,4,7

This parameter is used to separate pairings.

Parameter: PairingNameA,/,PairingNameB, d:hh:mm.

Enter comma separated Type A reference activity, "/", type B reference activities, time as d:hh:mm.

E.g. SbA/SbB,0:16:30

Separate reference activities by calendar days.

Syntax: TypeA,/,TypeB,Days

The parameter controls that the Day Off cover 2 local nights.

Syntax: night start,night end as HH:MM,HH:MM

This parameter is a hard constraint and it control the min and max values allowed. 

Specify a calculator span in minutes.

E.g. BLH,3600,4800 AR will not exceed 80 hours or go below 60.

Note: Be careful with the MIN value. If one of the loaded crew can't be above the MIN value, then the complete solution will be infeasible. The recommended MIN value is 0.

Enter comma separated Type A reference activity, "/", type B reference activities.

E.g. SbA/SbB. The Reference activity will not be assigned the day after.

This function controls the number of weekends off in a period.

Enter comma separated weekdays, number of weekends in the period.

Syntax: 6,7,3 (Saturday, Sunday, 3 weekends)

This objective tries to cover as many pairings as possible. 

Note: If this parameter isn't selected, no pairings will be assigned.

This objective tries to cover as many reference activity pairings as possible. 

Note: If this parameter isn't selected, no pairings will be assigned.

This parameter makes a fair distribution of the calculator inside the span. If the history days are applied, the Optimizer will make a fair distribution based on the full period (loaded plus history).

Syntax: BLH,3000,4800,30.