TRANSFER Installation and Management Guide

The TRANSFER Database and Depots
Introduction
13198 Tandem Computers Incorporated 1–5
In addition to folders and distribution lists that are associated with a private
correspondent depot, TRANSFER also supports shared access to folders and
distribution lists owned by an interest group. An interest group is a group of
correspondents who have a common interest or function; these correspondents share
access to group folders and can add their names to group distribution lists. Group
members can read items in a group bulletin board folder and save items to the
bulletin board for others to read. Each interest group has a group depot—with
profiles, folders, and distribution lists, like those for a correspondent depot.
TRANSFER automatically creates and maintains a special interest group called
PUBLIC at each node. All local correspondents are, by default, members of the
PUBLIC group and have shared access to the PUBLIC folders and distribution lists at
that node.
The Way Depots Work
Although TRANSFER correspondents care only about the external representation of
the data in their depots, programmers and system managers who are concerned with
the size of their database need to understand the internal structure of a depot. What
does it really mean for a profile or folder to be in a depot or for a package to be in a
folder?
A depot is not a single file. TRANSFER assigns unique IDs to depots, folders, and
items. The depot ID appears in records of various kinds, distributed over several files
in the TRANSFER database. The depot ID in profile and folder records shows that the
profile and folder are in that depot. The item ID appears in folder records and shows
that the item is in that folder.
Figure 1-2 illustrates the relationship of depots, folders, items, and packages in the
TRANSFER database. TRANSFER uses disk storage space efficiently by having no
duplication of data at a node. As the figure shows, items are stored only once in the
database, no matter how they are linked. The same item can be a component of
several packages; it can be stored in a folder and also be a component of a package; or
it can be in several folders, and the folders can be in different depots. Still, the item is
kept only once in the TRANSFER database.