User contexts are stored in extended, roll and heap memory. However, memory areas are also required in which data can be stored globally between user contexts. The SAP extended global memory (SAP EG memory) and the SAP paging memory are available for this purpose.
The SAP EG memory is used to store data across all user contexts. It is only relevant for use since SAP Kernel 4.6D (This data was previously stored in sub-areas of the SAP roll memory and had to be tediously copied with every context switch). Use of the SAP EG memory allows fast and copy-free switching based on mapping, as has already been implemented for the actual user contexts in the SAP extended memory since SAP Basis 3.0.
The size of the SAP EG memory is configured using the em/global_area_MB parameter. The recommended size for SAP Kernel 4.6D is 10% of the SAP extended memory. (The standard delivery size of 32 KB generally suffices for older versions). Don't forget, however, that the size of the SAP EG memory has to be subtracted from the size of the SAP extended memory in order to calculate remaining storage space for the user contexts and that is why you should not increase above this recommendation.