Functions of the R/3 Memory Management System

An application runs in an R/3 work process where an ABAP program is normally executed. The process requires memory to do this, which is allocated to it by the memory management system. The order in which the work process is assigned the memory type depends on the work process type, either dialog or non-dialog (see R/3 Memory Types), and the underlying operating system.

This is described in the section Allocating Memory for User Contexts.

The location of the various memory areas in the virtual address space is explained in Virtual Address Space of a Work Process.

The area of a user context that is directly accessible is now extended as needed, if the user context has expanded. For dialog work processes, the data of the user context, including internal tables, is located in this expandable area called Extended Memory. You can therefore access all the data in the user context. The data types Extract and Export to Memory remain in the SAP Paging.

The R/3 roll area is used for the initial memory assigned to a user context, and (if available) for additional memory if the Extended Memory is full.

The advantages of the SAP memory management require increased swap space and main memory. See: Operating System and Hardware Prerequisites.

The following diagram displays the memory types that can be assigned to R/3 work processes on the R/3 and operating system level. Here are the most important system profile parameters that control the availability of the memory types.

Whenever a dialog step is executed, a roll action occurs between the roll buffer in the shared memory and the memory area, which is allocated according to ztta/roll_first in a dialog process. Then the area in the shared memory is accessed that belongs to this user context.

The following illustration displays the roll process performed by the dispatcher.

• Roll-in: User-dependent data is rolled in from the common resource in the work process (and is processed there).
• Roll-out: User-dependent data is rolled out from the work process in the common resource (after the dialog step has ended).

The common resource stands for the different R/3 memory types: