Diagnosis
You have used a posting period as the periodicity forplanning step &V1&. A posting period can be clearly defined by enteringthe relevant fiscal year variant. You did not, however,do this when creating your planning step.
Assignments to info cube fields and planning scenario fields can onlybe created when the posting period is used as your time field type whenthe period has been specified completely, including a fiscal yearvariant. This therefore means that all assignments to the relevantplanning scenario fields are deleted when the fiscal year variant ischanged at a later date or when data is refreshed.

Procedure
To prevent unnecessary work, SAP recommends that all fiscal yearvariants be specified before assigning planning scenario fields to infocube fields.
You can define a fiscal year variant when defining your basic settingsat the planning step level.