Requested data cannot be locked (-> see long text)

What causes this issue?

Within a user context, you tried to set a lock request from BW-BPS and
then from BW Planning (or vice versa). As the respective applications
work with different buffers for the transaction data, they cannot both
be used simultaneously in a user context. This is because the determined
delta records in the respective buffer would lead to inconsistent data
in the database after saving: The determined deltas would cumulate.
Context information of the lock request:
The lock request can either come from BW Planning or from BW-BPS. The
context contains the following information:
BW Planning: <ZH>{InfoProvider}{query} </>for a lock request from a
query, <ZH>{InfoProvider}{planning function}{filter}</> for a lock
request from a planning function.
BW-BPS: <ZH>{planning area}{planning level}{planning package}{planning
function}{parameter group}.</> The following is valid for lock requests
from manual planning: Planning function = '0-MP' and the parameter group
is the techncal name of the planning layout.
The InfoProvider for the lock request is:
'&V1&'
The current BW-BPS context information is:
'&V2&'
The current BW Planning context information is:
'&V3&&V4&'

System Response

The data could not be locked.

How to fix this error?

Only use components from either BW-BPS or from BW Planning in a planning
application.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.