Principles of Operation

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# Principles of Operation

The DDM editor is used to create a Natural DDM from a database file or from another DDM. A Natural object (for example, a program or a data area) can only access a database file if a corresponding DDM has been created for this file and saved as a source object and a cataloged object. For further details on Natural DDMs, see Data Definition Modules - DDMs in the Programming Guide.

The following graphic illustrates the main features and basic principles of operation when processing DDMs with the DDM editor:

This section provides general information on storing and accessing DDMs and the restrictions that can apply to using DDM editor functions.

- Storing DDMs - FDDM System File

- Restrictions of Use

## Storing DDMs - FDDM System File

DDMs reside either in individual Natural user libraries or system libraries contained in the system file FUSER or FNAT, FDIC (remote environments on a z/OS platform) or FDDM. The FDDM system file is a separate container that collects all DDMs available in your Natural system environment. The FDDM system file is activated by setting the Natural profile parameter `FDDM` in the NATPARM parameter file.

Caution
If the FDDM system file has been activated, you can only store and access DDMs in the FDDM system file; DDMs contained in libraries in the FNAT or FUSER system file can then no longer be accessed.

In Natural Studio, DDMs are contained in the DDMs node of the tree view. Depending on the FDDM parameter setting, the DDMs node is either a subnode of a user library (FUSER) or a system library (FNAT), or represents the FDDM system file with the DDMs node located on the same level as the node User Libraries or System Libraries. In a remote environment located on a z/OS platform, the DDMs node represents the FDIC system file.

You cannot link DDMs contained in user or system libraries to an application. Therefore, in the Application Workspace, you can only use either DDMs from the FDIC system file (remote on z/OS) or the FDDM system file (remote on Linux).

DDMs are not restricted to files stored in an Adabas database. Some options described in the DDM Editor documentation only apply to Adabas and can be ignored if a different database management system is used.

#### Related Topics:

- System File FDDM in the Operations documentation

- FDDM - Natural System File for DDMs in the Parameter Reference documentation

## Restrictions of Use

The section below describes the restrictions that can apply to using DDM editor functions under:

- Predict

- Natural Security

### Predict

To guarantee data integrity for DDMs defined in Predict, the Predict administrator can restrict the use of DDM editor functions for editing, copying, creating, deleting and renaming, for which equivalent functions are provided by Predict.

In principle, we strongly recommend that you do not use any DDM Services functions that can alternatively be performed by Predict.

### Natural Security

Access to DDMs can be restricted when Natural Security has been installed. Within the DDM security profile, there may be a definition of whether a DDM may be modified only by specific users (DDM modifiers) or the owners of the security profile.

For further information, see Protecting DDMs On Linux And Windows in the Natural Security documentation.

### On this page

- Storing DDMs - FDDM System File
- Restrictions of Use