Field change &1 is not possible (transaction data already exists)

What causes this issue?

To ensure the consistency of existing data, you can only change object
&v1& if no <DS:GLOS.3526B2FCAFAB52B9E10000009B38F974>transaction
data</> exists in the change period; that is, neither plan data nor
actual data has been posted.
As transaction data already exists, it is not possible to change
objects in this time period.

How to fix this error?

If you still want to change the object, select a suitable change
interval by choosing "Edit -> Analysis period...".

Error message extract from SAP system. Copyright SAP SE.