I replied to your query on some other forum. Pasting that again:

SCP itself is a database for numbers and those numbers can access SCP services via SS7. In normal SSP-STP-SCP scenario, SS7 is not used to add numbers to the database but internal interfaces of SCP are used to create a number prior to assigning that number to some customer.

But in few cases SS7 can be used e.g.
a voice mail server is kinda small SCP. Whenever subscriber makes a call to voice mail, voice mail server creates an account for it in its database if the account do not exist already.