DDOs perform the operations Save, delete, clear/clear all and find. These operations are either initiated by a DEO sending a message to its server DDO or by custom code, which sends a message to the DDO.
Within a DEO, the operation is often initiated by users pressing a key, clicking on a button or selecting a menu item. For example, a user may press the F2 key, which will cause the Request_Save message to be sent to the DEO. The DEO will send a message to its DDO, also called Request_Save. The DDO will then perform the save.
When the programmer initiates the operation, code will be placed within a method that calls the appropriate DDO methods. This is described in Using Data Dictionary Objects in your Components.
Data Dictionary operations are performed on an entire DDO structure and never on a single DDO. This interaction is referred to as the propagation of DDO operations. It is very important to understand how the different operations cause DDOs within a structure to interact with each other. If you understand how the five major Data Dictionary operations behave, you can accurately predict how your program will behave.
Creating Data Dictionary Object Structures