Hi Vijaya,
Technically, when the Resource Utilization report is executed, liveCache Function Module /SAPAPO/OM_CAPA_PROFILE_GET is called.
As output of this FM, there is in internal table ET_PPDS_CAPA_ENTRY entries for each period and each resource containing what is the capacity supply during the period and how much of that capacity was used.
Example:
Resource From Time To Time Capacity Supply Capacity Used
WABCD 20160229230000 20160331220000 1209600.000 1000000.000
Based on entry above, the Resource Utilization report will show Available Capacity 1209600s / 336h / 14 days.Furthermore, Free Capacity = Supply minus used. Furthermore, Resource Load in % is Used divided by Supply.
So, the calculations done in PP/DS are pretty simple and based entirely on the data read from the liveCache.
If you want to dive deeper on PP/DS application logic executed to format the data for display in the report, you can analyze FM /SAPAPO/REPT_GETDATA_CAPLOAD.
Regards,
Tiago