If shuffling does not produce a complete block, the N-PBS Scheduler enters Denial Mode. If your bid has entered Denial Mode, it means that the system cannot award you a line honoring all of your bid preferences. Denial mode is an attempt by the system to award you a line honoring as many of your bid preferences as possible.
Denial Mode Bid Logic Example
This section describes how denial mode processes a bid.
The table at the bottom of the screenshot demonstrates the pairings available to this crewmember at their seniority level. The white squares indicate that a pairing has gone senior or not operating on that day, while the blue squares indicate what pairings are available to be awarded.
Regular Bid Award Attempt 1
The N-PBS Scheduler processes the bid and attempts to award a line. Bid preferences 2,3 and 4 remove all pairings from the available pairing pool (as shown in red). The scheduler attempts shuffling and trip substitution but still cannot build a full line. Because a line cannot be built the system enters Denial Mode.
Denial Mode Attempt 1
In the first attempt, the scheduler tries to build a line not using any Avoid or Prefer Off bid preferences. This determines if a line can be built at all. In this example, the scheduler can build a line without these bid preferences. This line is saved as the current best available line.
Denial Mode Attempt 2
In this attempt, the scheduler tries to build a line honoring bid preference 2. In this attempt, the scheduler cannot build a complete line. No new line is saved and the line from attempt 1 continues to be the best line available. The system determines that this bid cannot be honored and will no longer attempt to honor it.
Denial Mode Attempt 3
In this attempt, the scheduler attempts to build a line honoring bid preference 3 only. Bid preference 2 is not used because it has determined in the last attempt that it is impossible to build a line honoring bid preference 2. The scheduler has built a complete line using bid preference 3. The system now saves this line as the best line available.
In this attempt, the scheduler attempts to build a line honoring bid preferences 3 and 4. The scheduler uses bid preference 3 because it knows that it can build a line using the bid preference from the previous attempt. Bid preference 2 is not used because it has determined in attempt 2 that it is impossible to build a line honoring bid preference 2. This attempt has built a complete line that fits within the credit window assigned by the administrator. This is the best line possible honoring as many preferences as possible. The crewmember could not avoid pairings greater than 1 day but did manage to hold Saturday and Sundays off.
Denial Mode handles certain deniable bid preferences differently:
Prefer Off bid and Avoid Pairings bid preference options are removed one at a time if you have more than one option on the bid preference, such as a list of preferred days off. In this case, Denial Mode removes the date at the end of the list first, and works towards the left if it needs to delete additional days or dates. It handles the bid as if it were a series of separate bids as shown next.
Consider the following bid preference:
Prefer Off Jan 25 2019, Jan 26, 2019, Jan 27, 2019 / Prefer Off Jan 25 2019, - Jan 27 2019
Note: that Date List and Date Range Prefer Off Bids are processed the same as described below. This also includes multiple dates added to Avoid Pairings Bid Preferences such as Avoid Pairings if Depart On Jan 25 2019, Jan 26, 2019, Jan 27, 2019
In Denial Mode, this single bid preference is treated as 3 separate bid preferences (you will not see any changes to your bid).
- Step 1 - the scheduler attempts to build a line with Jan 25 off (any other bid preference already honored remains honored).If it is successful, the line with Jan 25 off is saved and stored as the current best line. If it is unsuccessful, the line is not saved.
- Step 2 - if Step 1 was successful, the scheduler attempts to build a line with Jan 25 and Jan 26 off (any other bid preference already honored remains honored). If step 2 is successful, it is stored as the current best line. If unsuccessful, the line is not saved.
- Step 3 - if step 2 was successful, the scheduler attempts to build a line with Jan 25, 26 and 27 off (any other bid preference already honored remains honored). If step 3 is successful, it is stored as the current best line. If unsuccessful, the line is not saved.
If any of these steps are successful, the system moves to the next bid preference (if any remain) and attempts to build a line with any preference honored.
So, if the scheduler cannot award you all 3 days off, you could get a line with 1 or 2 of the days off.
Bid Groups are independent of each other. Bid Preferences are only relevant for the bid group they are contained in. If the N-PBS Scheduler moves to another bid group it clears anything awarded from the previous one and begins processing the next bid group.
The following options and bid preferences are still honored:
All or Nothing - if the N-PBS Scheduler cannot honor all dates off on the bid preference, it won't honor any of the dates.
Else Start Next Bid Group (ESNBG) - the N-PBS Scheduler will move to the next bid group if it cannot honor a bid with this option attached. See Else Start Next Bid Group for more information.
Clear Schedule and Start Next Bid Group (CSSNBG) bid preference - the N-PBS Scheduler will move to the next bid group if a complete line has not been built when it reaches this line. See Clear Schedule and Start Next Bid Group for more information.
It is best practice to have a bid group below a bid group with the ESNBG or CSSNBG. You will receive a warning when you submit your bid if you have these options and do not have a bid group below it.
The N-PBS Scheduler tries to award pairings to reach the Threshold Value for a given Credit Window. However, as long as your block is above the Minimum Value, the N-PBS Scheduler does not go into Denial Mode to force your block above the Threshold Value.
The N-PBS Scheduler will abandon the current bid group and move to the next bid group if a bid preference with an Else Start Next Bid Group or Clear Schedule and Start Next Bid Group cannot be honored.
Administrators set the Minimum, Threshold and Maximum Values for Minimum, Normal and Maximum Credit Windows.
If you request a Minimum credit block (Set Condition Minimum Credit) or a Maximum credit block (Set Condition Maximum Credit), the N-PBS Scheduler WILL go into Denial Mode if the block is not above the Minimum Value, even though the block may be within the Normal Credit Window.
If Denial Mode cannot honor the Set Condition Minimum/Maximum Credit bid, the next completion attempt reverts to the Normal Credit Window.