====== Modifying a track ======

After a track has been created and used there is often a need for changes. Thankfully almost everything about a track can be changed: fields and rounds can be added, changed or deleted; track events and assigned organizations can be changed and even the track type can sometimes be changed.

However: not all changes are effective immediately. As thousands of tracks can be assigned to patients the process of adjusting these assigned tracks can take a long time and is therefore performed in a separate process: the assignment check.

===== Changes that never happen =====

When a survey has been answered the token corresponding to that survey will **never** be changed by the program. You can manually change these tokens, but otherwise token never change once they have been answered.

===== What happens at once =====

All **new** tracks will start using the new definitions at once, but for existing tracks only some changes have an immediate effect:

  - Changes to the survey definition in the source.
  - Changed field definitions will do nothing until someone or a process acts on those fields. Then the new definition will be used.
  - Changed round calculations will be used only when the track recalculates, e.g. after a survey was answered.
  - Changes in the use from and until fields as well as the organizations allowed to add the track will be effective immediately. Existing assigned tracks will remain active though.

===== Changes that need an assignment check =====

The assignment check can be performed in the Track builder for either a single track or for all tracks.

  - New tokens will be created for new rounds
  - Deleted ans inactive rounds will be removed if they have not been answered 
  - Rounds whose survey has changed will be updated, unless the survey has been answered
  - Changes to the round description and round order
  - All date calculations are performed using the new settings

===== Changes that need Field recalculation =====

Some fields, e.g. appointment fields and location fields can be defined to be filled automatically. 

Once this definition is changed the fields are recalculated the next time the fields change, but you can apply this recalculation manually in the Track builder for either a single track or for all tracks.

This process will not automatically create new tracks when automatic track creating is enabled. That check only occurs when an appointment is changed.