Memory Types
The memory management system assigns memory to a work process. The different memory types are:
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Extended memory
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Private memory (heap memory)
The sequence of allocation depends on the type of work process and the configuration.
The user context area that allows direct access can be extended as required when the size of the user context increases.
Use
Extended Memory
The large part of the user context is stored in the extended memory. Page management of this memory stack is performed directly by the SAP system, and not by the operating system. The extended memory is implemented as an unnamed mapped file (on AIX and optionally on HP-UX as shared memory). This means the virtual address space uses the swap space of the operating system as background memory.
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 private memory. This is known as heap memory because it is specific to the process, and the user context can no longer be processed by a different work process.