A package is a piece of a model. When working with large models, you can split them into smaller subdivisions in order to avoid manipulating the entire model at once. Packages can be used to organize your model into different tasks and subject areas, and to assign parts of it to different development teams.
You can create as many packages as you need in a model. The name of each package must be unique in the model. You can decompose a package into other packages, and there is no limitation to the decomposition depth.
Packages can contain the same kinds of items as models:
In the example below, a package called "Lending Records" (with a diagram of the same name) has been added to the model "Library OOM":
Note that you cannot save a package individually. When you save the model you also save all the packages it contains.