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#### 8.5.1 Introduction to PolyORB/DSA

A distributed Ada application comprises a number of partitions which can be executed concurrently on the same machine or, and this is the interesting part, can be distributed on a network of machines. The way in which partitions communicate is described in Annex E of the Ada Reference Manual.

A partition is a set of compilation units that are linked together to produce an executable binary. A distributed program comprises two or more communicating partitions.

The Distributed Systems Annex (DSA) does not describe how a distributed application should be configured. It is up to the user to define what are the partitions in his program and on which machines they should be executed.

The tool `po_gnatdist` and its configuration language allows the user to partition his program and to specify the machines on which the individual partitions are to execute.

`po_gnatdist` reads a configuration file (whose syntax is described in section The Configuration Language) and builds several executables, one for each partition. It also takes care of launching the different partitions (default) with parameters that can be specific to each partition.