Conversion of the leading currencies may lead to problems (->long text)

What causes this issue?

The standard setting for copying costs or prices is the transaction
currency or controlling area currency. Note that converting the leading
currency can lead to unrequired effects, for example:
You are copying costs with the controlling area currency as leading
currency, although all currencies are active on the database (see
transaction <DS:TRAN.OKKP>Settings in controlling area</>). If data
exists, whose keys are only differentiated by the transaction currency,
the difference is ignored and both records are summarized in a new
record. It is essential that a planning in transaction currency is also
copied with the transaction currency as leading currency.
You are copying costs with the object currency as leading currency. You
should check that all objects in the target version use the same object
currency as the corresponding object in the source version.

System Response

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

How to fix this error?

You can change the settings for this message in Customizing by
choosing: Controlling -> General Controlling ->
<DS:SIMG.SIMG_CFMENUORK3OBA5>Change Message Control</>. Enter the
following settings:
Enter "GP" as the application area.
For message 859, enter the desired message type for online processing.
To do this, use the following code:
Message type,,ID
Error message,,E
Note in window,,I
Warning,,W
No message,,-

Error message extract from SAP system. Copyright SAP SE.