Extended Memory Management in R/3
ASAP World Consultancy
SAP R3 developers have to know and understand the architecture of the product. This tip, excerpted from InformIT, discusses how extended memory management works, and the context of R3 user sessions.
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R/3 Release 3.0 introduced an extended memory capability that permits a more intensive use of virtual memory. Reservations for roll and paging areas are no longer necessary and have been replaced by the R/3 user session context system.
When a work process is conducting activities as part of a step in a user dialog, it needs ready access to a set of data elements. These elements are the user session context.
If another work process is assigned to the next step in the dialog, the information now in some or all of the data elements of the first user session context must be made available to the second work process. The second user session context may also require additional information.
Before Release 3.0, user session context information was transferred by the roll-in, roll-out method of copying information. This took a great deal of time and many system resources.
In Release 3.0 and later releases, the data needed by subsequent user session contexts is accessed not by copying, but by mapping.
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The information transferred to the subsequent dialog step is not the actual data, but a set of pointers that indicate where that data can be found. Thus, a very complex data structure can be addressed or mapped for use by a work process by the transfer of a simple mapping pointer message.
Using mapping rather than copying in this context is expected to provide a much faster response time and, in certain installations, the possibility of handling larger loads without adding application servers.
Developments in virtual memory made possible by 64-bit architecture are expected to extend the benefits of the mapping concept.
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To read more of this tip, click over to InformIT. Registration is required, but it's free.
This was first published in January 2001
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