The question “what is it doing and why ?”is a pretty standard part of the BASIS person / teams day. It can be in the context of debugging a program or process, or trying to work out what configuration changes are required to make something work. An example of when thius gets escalated to BASIS is when the development or functional team have moved on, leaving someone who knows what to do but not why – usually a user (under pressure from their boss) who just wants to get the system doing what they’ve been told it should be doing….
However, your BASIS team (or person) has to be a jack of all trades, but also a working knowledge of Networking, Desktop PCs, the Operating System(s) and Databases(s) their SAP systems are running on and so on, as well as being able to answer SAP functional questions.
Early last centrury, when I worked on IBM mainframes, I found that the secret to finding anything in the IBM technical library was knowing the structure of the library. Nowadays, the best way of dealing with this need to know something about everything is not by trying to know everything, but by knowing how to find out everything. An example of this is how I track down what tables and fields lie behind an SAP transaction.
PF1 on the field you’re interested in
This is the standard answer. For simple programs, it works well. However, very often, it will point to a field or structure that bears no relationship to a database table or field. In other words, it tells you exactly the source field and structure, but it won’t tell you how that field was derived.
Use a Different Field
If the technical information pop up shows a structure and not a real field, just try another field on the same area of the screen. It is surprising how often this works !!
Use ‘Where Used‘ on the Data Element
From the technical information pop up, select the data element then press Navigate to get to the Data Dictionary. Once there, press the Where Used button.
Transactions SE30 Runtime Analysis and ST05 SQL Tracecan be over-kill for determining what fields and tables are being used, but can be used to see how (for example) configuration data controls how and / or when the fields and tables are updated. It’s also useful when dealing with Z or Y code, structures and tables.
SE80 Object Navigator
This is probably more useful for a functional person, and is not available on the older SAP releases anyway. However, if you know the program behind the transaction, you can use SE80 to find all the Data Dictionary objects (including tables and fields) associated with that program.
This is for when you have the need (or time) to get a much broader understanding of an area of SAP. The exact method depends on your SAP release. For example, if I wanted to find a bit more about the 4.6c SAP Office when it handled appointments, I might start off with transaction SSC1 Maintain appointments diary. Using System –> Status, I get the programs name SAPLSCA2 which I copy to the program field of transaction SE38 and select the environmental analysis option, to get a list of objects to analyze for.