You must make an entry in parameter IRKU01_CUR or IRKU02_CUR.

What causes this issue?

The parameter IRKU01_CUR or IRKU02_CUR in the planning data interface
does not contain an entry. This may be because you transferred a
planning parameter in field RPLAN and have not changed this entry for
4.5A. The planning parameter is not supported as of Release 4.5A.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.