abap/heap_area_total: Total Quota for Heap Memory 
This parameter determines the upper limit of heap memory in bytes available to all work processes of an SAP application server. You can use this upper limit to restrict the swap space usage of an SAP application server to a specific amount. You can find more details on this topic under Functionality of the SAP Memory Management System.
Integration
The graphic below shows the relationship with the parameters abap/heap_area_dia, abap/heap_area_nondia, and ztta/roll_extension.
Activities
The value is specified in bytes.
The default value is platform-specific and is determined dynamically. This is the default value specified in transaction RZ11. This value should not normally be changed.
Note
This value ensures that even at maximum swap space usage of the SAP system and during normal operation, at least 100 MB swap space (or approximately 10-15%) remains free. See also Swap Space Requirements.