In the former case, a level of indirection is required to look up the physical address of
the object on disk. In both cases, however, an OID is different in size from a standard
in-memory pointer that need only be large enough to address all virtual memory. Thus, to
achieve the required performance, an OODBMS must be able to convert OIDs to and from
in-memory pointers. This conversion technique has become known as pointer swizzling
or object faulting, and the approaches used to implement it have become varied, ranging
from software-based residency checks to page faulting schemes used by the underlying
hardware (Moss and Eliot, 1990), as we now discuss.