SHADOW MECHANISM FOR A MODIFIABLE OBJECT ORIENTED SYSTEM

A computer system is disclosed which includes a read only memory in which a first version of a data element is stored, a random access memory in which a second version of the data element is stored, and a shadow system for transparently determining whether to access the first or second version of the data element. In the disclosed system, separate areas of memory are maintained for a committed version of the data element and an uncommitted version of the data element. Bottleneck commit routines only allow the uncommitted version to become the committed version of the data element at certain times, such as when the data are not subject to modification. By disposing of the version of the data elements in the uncommitted area, the system effectively reverts to the state it was in at the time changes were last committed from the uncommitted area to the committed area.