the size of an Oracle database for SAP varies based on a lot of items. Which modules are to be installed? How many “bolt ons”? Is the data to be transferred from an old system and migrated into this one? Are you planning for growth? ……..
Currently we have an SAP database which is approximately 1.2 Terrabytes and grows by 20 Gb monthly. This database started as approximately 300 Gb in 2000, but has been updated twice and new modules/bolt-ons have been added.
I would work with SAP and your basis team to determine a good initial size estimate.