Hello TW
In some cases it is necessary to open a customizing transaction on a productive system.
The most common case is the creation of MRP controllers and I wrote the following document about that:
Open a customizing transaction for changes on the productive system
Answering to Prasad, there is no official list of all the error messages but you can find them on table T100. In some cases the error messages can be changed in customizing but sometimes, they are hardcoded as errors. The following document explains how to check that in debug:
How to analyze an error message in debug
BR
Caetano