BRF expression '&1' cannot be calculated

What causes this issue?

Expression &v1& uses the CASE expression &v2&. An error occurred during
the attempt to crate a data object of BRF type &v3&.

System Response

The system cannot create any data object.

How to fix this error?

Call up transaction BRF.
Enter the application class &v4&.
Check the following with BRF expression &v2&:
Result type
Field/structure length
Decimal places

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.