No free numbers found for indexed perform

What causes this issue?

The number interval for the indexed perform is used up.

System Response

Creating the function or operation is not allowed.

How to fix this error?

As a solution, you can use the international standard subprogram
FUXCALL. In the future, every function that has entered this subprogram
as the ?name of the self-defined form routine? in transaction PE04
(maintenance functions and operations) is assigned the value 170 (= Hex
AA) when the schema is generated.
In FUXCALL, the subprogram FUXCALL_NATIO is called for countries, and
the subprogram FUXCALL_CUST is called for customers. You can use a
statement CASE AS-FUNCO. to jump to the actual coding for your new
functions (use the name that you entered in PE04 instead of FUXCALL for
the form routine).
If you use the standard name suggested in PE04 for your form routine
(this is only possible for the special characters _ - $ % in the
customer namespace), you do not have to implement FUXCALL_NATIO or
FUXCALL_CUST.
Note that the performance may worsen for functions created in this way
since the indexed perform is no longer directly used for the jump.
However, this will only affect performance, if the function is called
regularly in your schema (for example, in a net iteration).
This also applies to operations with the subprograms OPXCALL,
OPXCALL_NATIO, and OPXCALL_CUST, and the statement CASE OP-OPCOD.

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.