The single address space incorporates all memory objects on all nodes in a distributed system. There are no user-visible memory hierarchies, no file system. Any memory object is potentially persistent, i.e. can outlive its creator process. All objects are uniquely identified by their virtual address, which is a 64-bit number.
Any object is potentially accessible by any process, provided the process is authorised to do so.
As there is no file system, all the secondary memory in the system is nothing but paging store. If a process references a non-resident object, the kernel will obtain a copy and store it in local primary memory. This is not different from paging in traditional VM systems, except that a page may be obtained from disk or across the network. An object is the unit of protection. No other structure on objects is assumed by the system, but higher software layers are free to impose structure.