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The memory management system assigns memory to a work process. The different memory types are:

  • SAP roll area

  • SAP extended memory

  • Private memory

The sequence of allocation depends on the type of work process and the configuration.

For more information, see Allocting Memory for User Contexts (UNIX)

The user context area that allows direct access can be extended as required when the size of the user context increases.

For more information, see User Context


Roll Area

The roll area is used for additional memory (if available) when the extended memory becomes full, as well as for the initial memory assigned to a user context. The limits are set using parameters.

Extended Memory

The large part of the user context is stored in the extended memory (EM). Page management of this memory stack is performed directly by the SAP system, and not by the operating 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.

When the context is changed, the user context, which is in the extended memory, is not copied as with the roll area. Instead it is allocated 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 input/output operations when accessing internal tables and lists is no longer needed. The result is low CPU usage and shorter access times.

Private Memory

If the extended memory is fully occupied, or the limit for the work process has been exceeded, the work process allocates heap memory. This is known as private memory because it is specific to the process, and the user context can no longer be processed by a different work process (PRIV mode).

Caution Caution

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.

For more information, see Swap Space Requirements

End of the caution.