QUESTION
 When I try to save a part, I am getting an error that states
 that there is no primary part?

ANSWER
 This can happen assuming the following order of actions:
    1. open a new part (the default window is the primary part)
    2. add, for example, a notebook (the default window is still the primary part)
    3. delete the window (no primary part)
 From here, an attempt to save will generate a warning until you
 specify which part is to be the primary one.

 However, if the order is the following, the result is different:
    1. open a new part (the default window is the primary part)
    2. delete the window (no primary part)
    3. add the notebook (the notebook becomes the primary part)

 From here, saves will work fine.

 In summary, if the primary part is deleted, VisualAge makes no
 assumptions about which part should now become the primary one.  If
 however, you add a new part when no primary part is currently defined,
 the newly added part becomes the primary part.  Note that it must
 be a visual part when editting a view class otherwise primary part
 will stay undefined.  The rationale for automatically setting
 primary part when one is not currently set was to simplify the typical
 scenario where one wants to substitute the window for an
 embeddable window (Form).