.PLL The library .PLL file contains both library source code and the compiled, platform-specific p-code (executable code). The .PLL file is created or updated when you save your library module. In addition, when you save your library module, the changes are reflected in each module to which the library is attached.
.PLX The library .PLX file is a platform-specific executable that contains no source.
When you are ready to deploy your application, you will probably want to generate a version of your library that contains only the compiled p-code, without any source. You can generate a .PLX file from Oracle Forms or from the command line.
Note: When you attach a library to a module in Oracle Forms, you attach the .PLL version of the library. At runtime, Oracle Forms looks for a .PLX file by that name in the default search paths. If no .PLX file is present, Oracle Forms looks for the .PLL file by that name.
.PLD The .PLD file is a text format file, and can be used for source-controlling your library files.