To understand database tables in special database SAP better, we have to first understand SAP's architecture. Here is a small glimpse into SAP's 3-tier architecture. This is the UI layer. When you log into SAP using the SAP GUI, this GUI can be called the UI layer. You can also log in using the browser based Web UI.
: This is the Application Server special database Layer. This is the core of SAP. This comprises of the runtime environment of SAP. At a high level there is a dispatcher that looks at the incoming request from the special database front end and allocates a work process ( WP ) to take care of the request. There are a lot of other processes involved in SAP's runtime environment and they are beyond the scope of this ABAP tutorial. For now it special database suffices to know that an ABAP program's runtime environment is in the Application Server's memory.
and as long as you use one of those special database in tier-III SAP will work. Now, we all know that each of these databases have their own versions/flavors of SQL. So when SAP's Application server interacts with the database layer, it talks via the "Database Interface" or simply DBIF. The task of DBIF is to ensure that it converts SAP's special database Open SQL into native SQL understandable by the corresponding database.
Without going much further into SAP's special database architecture, let's start by creating a database table in SAP. Let's try to create a database table "Customer" as follows. That's a very simple database table. You might have special database immediately noticed a peculiarity. Why did I define the database table name as "ZCUST" as opposed to saying "CUST"? To understand this, we have to first understand the concept of SAP special database Namespace.