Library

A  PL/SQL  library  is  a  set  of  program  units,  involving  user-named  procedures, functions and packages. A PL/SQL Libraries gives a convenient means of storing client-side program units and sharing them between multiple applications.

Once a PL/SQL library is created, it could be attached it to any menu or form. The program units stored in the PL/SQL library could be known as from triggers and menu item commands, user-named routines written in the form or menu module to that the PL/SQL library attached.
The similar PL/SQL libraries can also be attached to other PL/SQL libraries. Whenever a PL/SQL library is attached to another PL/SQL library, program units inside the attached PL/SQL library can be referenced in the current library.

PL/SQL libraries support dynamic loading. A Program unit is loaded into a computer’s memory only when an application requires it. This can significantly decrease the runtime memory requirements of an application, but tends to slow an application. The trade off is between memory vs. speed usage.