Basic DDM concepts

 

This topic collection gives the basic concepts of DDM.

Because remote file processing is much like local file processing, these topics should provide sufficient conceptual information for most users of DDM. Another topic provides additional, more detailed concepts, and the topic Additional DDM concepts is intended primarily for the experienced programmer who wants or needs to know more about DDM.

From an user's viewpoint, accessing data on a remote system is much the same as accessing data on the local system. The main difference is the additional time needed for the data link to pass the data between the systems whenever the remote file is accessed. Otherwise, the user or application program does not need to know whether the data being accessed came from a local or remote file. Refer to Performance considerations for DDM for additional considerations.

For DDM iSeries™-to-iSeries file processing, remote file processing is done much the same as local file processing. The purpose of this topic collection is to describe the things that are different for DDM. Also, because other systems can use DDM, those considerations and concepts are covered as needed to enable the iSeries programmer to successfully prepare the server for using DDM.

The DDM concepts in these topics describe mainly iSeries-to-iSeries remote file processing. For purposes of illustration, concepts that relate to System/36™ and System/38™ are shown in some examples. If you are using DDM on both System/36s and iSeries servers, you should be aware that the concepts for both types are similar, except in the way they point to the remote file: An iSeries server and a System/38 use a separate DDM file to refer to each remote file to be accessed; System/36 uses a network resource directory that contains one network resource directory entry for each remote file to be accessed.

Although DDM supports other functions besides opening and accessing remote files, the concepts described in this topic collection deal primarily with remote file accessing.

 

Parent topic:

Introduction to i5/OS DDM

 

Related concepts

Additional DDM concepts
Performance considerations for DDM