use the Repository Information System to find out where objects are used 

Access the ABAP/4 Repository Information System. To do so, select Tools ® ABAP/4 Workbench in the initial screen of the R/3 System. In the ABAP/4 Development Workbench, select Overview ® Repository Info Sys.

To find out where modeling objects are used, position the cursor on Modeling and select the menu options Edit ® Expand subtree. Under the heading Data modeling, you will find all the points relating to the Data Modeler, namely Data models, Entity types, and Entity type attributes. Click on Data models or Entity types and select Repository Infosys. ® Where-used list.

A dialog box appears in which you have to enter the name of the object for which you wish to see a where-used list. In the case of entity types, you also have to specify which type of where-used list you require (i.e. for use in data models or in tables). Once you have done so, click on Cont. A hit list is displayed.

You can execute the following functions from within this list.

• You can access the display screen for an object by selecting the object you are interested in choosing Display.
• You can access the maintenance screen for an object from within the list by selecting the object in the first column of the display and selecting Change.
• You can display the occurrences of an object from the list in other objects by selecting the object and choosing Utilities ® Where-used list.