Collective processing not possible due to processing by user &

What causes this issue?

Several objects are to be processed in parallel (copy, delete, and so
on). In this case, no other user may process these objects in the same
controlling area or chart of accounts. User &V1&, however, is
processing groups in the same controlling area/chart of accounts
(&V2&).

System Response

The function is not executed.

How to fix this error?

Perform the required function later or get user &V1& to complete his
processing session.

Error message extract from SAP system. Copyright SAP SE.