How validate all mapping in repository ?

1. In repository go to menu “tool” then “queries”. Query Browser dialog box will appear.Then click on new button.
   
   
2. In Query Editor,  choose folder name and object type as I have shown in the picture.
   
3. After that, execute it (by clicking the blue arrow button).
4. Query results window will appear. You select single mapping (by selecting single one) or whole mapping (by pressing Ctrl + A) and go to "tools" then "validate" option to validate it.