"What are the disadvantages of a Hammer?"A slew of loud, annoying songs?
a rule where using the hammer is using the wrong tool for the job.You must never have held a hammer. When holding a hammer, everything because so clear. Everything needs a hammer.
Like driving in screws.That would be an odd sight. Though, it would give a new definition to "going for a spin".
Using it to stir a mug of coffee.Let's see, Bob buys coffee. I want to see Bob become bereft of said coffee, without confronting him directly. Angrily, i walk over to Joe and ask him to relieve Bob of his coffee. Joe balks at me. So, i wave my hammer wildly at Joe, and Joe gets to work.
1. It execute all package unit when we call subprogram of a package.That'd would be unexpected. perhaps you mean "loads all package unit"
2. Cache compiled program.Surely an advantage?
3. Difficult to maintain if package is become lengthy.As opposed to hundreds of separate procedures?
4. Specification persist without body.Allowing you global variables and type definitions. Again, a plus.
There are no inherent disadvantages. Most of things user630688 lists could just as easily feature in a list of advantages of packages. And the size of packaged code is down to proper design more than anything else.As you can see from the humorous responses, there are no disadvantages.