SAP Memory Types

Definition

The memory management system assigns memory to a work process. Here are some of the various memory types:

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SAP Roll Area
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SAP Extended Memory
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Private Memory

To find out the order in which memory type is assigned, refer to Allocating Memory for User Contexts.

The area of a User Context that is directly accessible is now extended as needed, if the user context has expanded.

Use

For dialog work processes, the data of the user context, including internal tables is located in this expanded area. You can therefore access all the data in the user context. Only the data types Extract and Export to Memory remain in the SAP Paging.

The roll area is used for the initial memory assigned to a user context, and (if available) for additional memory if the expanded memory is full.

The majority of the user context is stored in the extended memory. Page management of this memory as a stack is not taken from the operating system; rather it is performed directly from the SAP System. This extended memory is implemented as an unnamed mapped file (on AIX and optionally on HP-UX as shared memory). This means the address space uses the paging file or uses the swap space of the operating system as background memory. For more information, please see the platform-specific documentation.

With the context change, the user context is not copied as with the roll area. Instead it is assigned to alternating work processes by mapping operations. The roll area can be decreased, which results in a faster context change because less data is copied and mapping an extended area is not work-intensive.

All internal tables and ABAP variables are located completely in the area of a user context that can be directly addressed. Copying and in/output operations when accessing internal tables and lists is no longer needed. The result is low CPU usage and shorter access times.

The advantages of the memory management system require increased swap space and main memory. The need for swap space increases because full-sized internal tables and lists are in the address space and take up swap space. The main memory requirements may increase to prevent excessive operating system paging due to the increased swap space requirements.