This parameter restricts the amount of heap memory (Private Memory) that an SAP non-dialog work process can allocate. This value refers to spool, update, and background processes. This value ensures that enough swap space is available in the system.
Local memory is hardly needed any more with modern 64 bit platforms, as the memory requirement can be satisfied by the SAP Extended Memory.
The graphic below shows the relationship with abap/heaplimit.
If the value of abap/heaplimit has been reached, the work process is restarted after the dialog step has ended. If the consumption of heap memory exceeds the quota abap/heaparea_(non)dia, the user context being executed at this time is cancelled before it can be completed.
You can use this quota to prevent one single non-dialog work process (user context) from filling the entire heap memory of the application server.
The work processes of an application server can allocate only so much heap memory as specified in parameter abap/heap_area_total. The limit specified in the parameter refers to the combined heap memory usage of all work processes for an application server.
The value is specified in bytes.
The default value is platform-specific and is determined dynamically. The default value is specified in transaction RZ11. This value should not normally be changed.
The value should be high enough for the largest possible background processing context in your SAP system. If the value is too small, SAP Extended Memory is assigned to the background process. This extended memory is not available for dialog work processes. See Allocating Memory for User Contexts.