A VOB (versioned object database) is a data repository that holds the files, directories, and any objects that collectively represent a product or a development effort.
As the project manager, when you use UCM as the process for managing your projects, you are responsible for setting up the project environment, referred to as a UCM project. During the creation of the UCM project, Rational ClearCase creates the project VOB as well as the development and integration streams. This subject is covered in the module Setting up a UCM project.
When you use base Rational ClearCase, you have to create the VOBs manually.