Implementation on Windows 
The basis for the Zero Administration Memory Management on Windows is the dynamic extended memory. The technique provides you with a nearly unlimited memory resource. Initially, the extended memory is set to the size of the profile parameter PHYS_MEMSIZE [PM]. If the user requires more memory, extended memory extends itself in steps from "[PM] / 2" up to the set limits in the profile parameter em/max_size_MB, or until the address space in the Windows page file is used up. By setting the default value for em/max_size_MB to 20000 MB for 32-bit, and 100000 MB for 64-bit Windows platforms, the size of the Windows page file represents the actual limit for extending the extended memory. The profile parameter PHYS_MEMSIZE determines how much of the total main memory is used by the SAP system. The default value for PHYS_MEMSIZE is the size of the main memory [MM].
The memory allocation strategy for a nondialog work process was changed as of Release 4.0B. Through the previous allocation sequence, the extended memory was protected to the benefit of the heap memory. This is no longer necessary when using the dynamic extended memory, and the allocation sequence of the batch work processes is identical to the sequence of the dialog work processes. Another beneficial side effect is that you can avoid the PRIV mode (see Private Memory) for background work processes and starting the work processes).
Sequence of allocating memory for nondialog work processes:
Roll memory until the limit ztta/roll_first
Extended memory until the limit min {em/address_space_MB, ztta/roll_extension}
Roll memory until the limit ztta/roll_area
Heap memory until the limit abap/heap_area_nondia
The basis for zero administration memory management is a sufficiently large Windows page file. For more information about the Windows paging file size, see the installation guide for your SAP product.
All relevant memory management parameters are set with an optimal default value so that all manual configurations are unnecessary.