Abstract: A method and apparatus for efficiently accessing data in a system in which changes of program releases must be accommodated. Data is accessed via one of two indirect data accessing tables. When a new release is introduced into a system, and the new release is activated, a switch is made to an indirect data accessing table which points to the data to be used by the new release. The previously active data accessing table is maintained in case it is necessary to switch back to the old release. After the new release has been accepted, the contents of the second indirect data accessing table are copied into the first indirect data accessing table, and the first indirect data accessing table becomes active. Advantageously, only the data blocks which include changes need to be initialized, and the process of accessing data remains highly efficient.