RSTMSCBU is a standard Executable ABAP Report available within your SAP system (depending on your version and release level). Below is the standard documentation available for this report and a few details of other objects it interacts with such as tables, function modules, includes etc. If you would like to see the full code listing simply enter RSTMSCBU into the relevant SAP transaction such as SE38 or SE80.

RSTMSCBU-1

 

RSTMSCBU-2

 

RSTMSCBU-3

 

RSTMSCBU-4