OSI/FTAM Programming Guide

ISO FTAM Concepts

HP NonStop OSI/FTAM Programming Guide—528612-001

2-24

File-Access Data Units

You access files by way of file-access data units (FADUs), which correspond to

subtrees; that is, a FADU includes a node and all of its children. Figure 2-6 shows

several examples of FADUs. The FADU corresponding to the entire tree (FADU 0)

provides access to the entire file. Other FADUs provide access to parts of the file.

The NonStop FTAM implementation does not use complex FADU structures like most

of those illustrated in Figure 2-6. In NonStop FTAM, FTAM-1 and FTAM-3 documents

are unstructured files consisting of a root node with a single associated FADU (similar

to the root-FADU 4 path shown above). FTAM-2 document types are flat files

consisting of a root node and a number of leaf nodes, each with an associated FADU,

or record.

Figure 2-7 on page 2-25 illustrates the NonStop FTAM FADU structure for FTAM-1 and

FTAM-3 documents, and Figure 2-8 on page 2-30 reflects the NonStop FTAM FADU

structure for FTAM-2 documents.

Figure 2-6. FADU Structure of Hierarchical File Model

VST0206.vsd

Root

FADU 2

FADU 3

FADU 1

FADU 4

FADU 6

FADU 5

FADU 0