Approximation of the Hardware resources required to support a particular software application.
To do this there are many ways.ground level-->Firstly from the software product view ---Will know more about customer requirements,sizing questionnaires & calculate the resources from the experience side (experience->always working on sizing will be able to give the rough estimate)
But Most of the companies provide there own various tools for the sizing like IBM.Oracle,SAP quick sizer,HP -Unix.They would say for free though but again If you need the accurate resource you need to pay for it .....
From SAP point of view
The SAP going live Functional upgrade check which consists of several sessions and is part of SAP standard support ensuring basic safeguarding of customers upgrade projects where Certified Consultants perform each session through a remote connection.
For example the values of one system which need to be upgraded from 47E to ECC6 .Regarding system environment. Central instance has 34 cpu's on HP-UX with 143 GB memory & 6 appservers on linux each with 8 cpu's & around 31Gb of memory ,Db size is of 6 Terabytes..Note 0901070 note gave a very good explanation of the effect on system hardware after the upgrade & satisfied with my result after reading various documentation.
