What is RGUGBR00 ?
Program RGUGBR00 is used to regenerate ABAP coding under SAP validation (OB28) and substitution (OBBH).
Sometimes, you have updates SAP validation and substitution and system doesn't work properly. What you have to do is just hit the button to run this program every time that you have updates SAP validation or substitution.
When you need to run RGUGBR00 ?
It is common in SAP FICO module that you may need to update SAP Validations (OB28) or Substitution (OBBH). But once you transport validations or substitution into your production system, DO NOT forget to run program RGUGBR00.
How to run RGUGBR00 ?
You need to run program RGUGBR00 every time that you have an update on validation or substitution. What you have to do is following this step:
First, you need to hit T-Code : SE38/SA38 and input program name. Please remind that this program doesn't have transaction code. You need to access this program via SE38 or SA38.
You will see many checkboxes in this screen. Don't worry, just select all of checkboxes except the last one "Trace prog. generate calls".
Then, hit execute button!
This program will regenerate ABAP coding under SAP validation and substitution and make everything works fine.
Summary
From my point of view, it is better to run this program every time that you transport SAP validation or substitution from your test environment to other environment. Some may create a schedule job to run this program daily.
Related SAP OSS Note
2512768 - Schedule the program run for RGUGBR00 after a successful transport request
842318 - Frequently asked questions about validations and substitutions