em/global_area_MB: Size of Extended Global Memory 

Use

This value specifies (in megabytes) the maximum size of that part of extended memory (see also parameter em/initial_size_MB) that is reserved for global data, that is, user-independent and work process-independent data. The amount of data involved is comparatively small (a percentage of the whole extended memory pool), because only administration data belonging to internal communication between SAP kernel components (task handler, enqueue) is stored in the global area.

The parameter should be approximately 5 – 10% of the parameter em/initial_size_MB.