Validation/substitution: Programs should be regenerated

What causes this issue?

The generation of the main program for validations, substitutions, and
rules in all clients is completed, but no code was regenerated for the
individual validations, substitutions, or rules. Normally, the system
continues to function error-free using the old code.

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?

In order to prevent possible errors, regenerate the code for your
validations, substitutions, and rules.
Upon complete of the upgrade, execute report RGUGBR00 for all clients
in which you currently use validations, substitutions, or rules.
Select these parameters:
"Generate rules"
"Generate validations"
"Generate substitutions"
"Generate sets"
"Generate rule usage"
"Generate validation usage"
"Generate substitution usage"

Error message extract from SAP system. Copyright SAP SE.