RAM Funda - SAP (RAM Recommendation for SAP)

RAM:
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UNIX: Note 146528
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A swap space size of 3 to 4 times the RAM size is recommended, even though a swap space of 10 GB or more might have to be created. The virtual memory available for a process is divided into "shared memory" and "local memory". All processes of an instance can access the shared memory, while only one process can access the local memory.

Most memory used in the R/3 environment is shared memory. Experiences has shown that the memory used is divided into 80% shared memory and 20% local memory.

In individual cases, there might be exceptions to this rule. Shared memory restrictions by the operating system affect the configuration options of the R/3 System drastically. The shared memory includes all R/3 buffers, such as program, table, roll buffers and R/3 extended memory.

The local memory includes the local memory of the work processes or heap.

In the 32-bit technology used so far, it is theoretically possible to address a maximum of 4 GB of memory from one process. Since a lot of memory cannot be used at all due to fragmentation effects, the memory that is actually available to an R/3 work process is much smaller in practice. The following sections specify the restrictions for some operating systems.

With the 64-bit technology, the above problems are solved. In 64-bit technology, an address space of many terabytes is available to a work process. To be able to use the 64-bit technology, you need a 64-bit operating system, a 64-bit version of the database software, and a 64-bit version of the R/3 kernel.

Compared to the 32-bit version, the 64-bit R/3 kernel has no new functions.
Compared to the 32-bit version, using the 64-bit version remains the same for users and administrators. Memory management becomes considerably simpler when you use the 64-bit kernel as compared to the 32-bit version.

Details can be found in Note 146289.