How do one decide "how much live cache one needs to implement APO in totality as well as only implementing DP functionality"?
The best solution is use SAP's Quicksizer which allows you to enter estimated volumes of DP data as well as data for all of the APO modules. The output of this is an estimate not only for live cache but also disc and CPU. Go to http://service.sap.com/quicksizer, but you will need a Sapnet logon and a customer number. If you are an existing SAP customer you should have both of these, but if you need any help you can email me firstname.lastname@example.org.
This was first published in January 2003