If a package, an object or a stored procedure is invalid you have to compile one to make it work.
The whole package is considered invalid if its specification contains errors. An object status is also determined by the validity of its specification. Project body or object body becomes invalid if at least one procedure or function that makes up the body is invalid. Stored procedure or function is invalid when its code contains errors.
PL/SQL programs can be compiled by right-clicking the node in the Database Explorer window, and choosing corresponding command from the Compile submenu of the shortcut menu. You can compile PL/SQL programs with or without debug information.
When working with Oracle server 10.1 or higher, you can enable compilation warnings. By default compilation warnings are ignored. To enable them, perform the following steps:
After performing these steps you can work with PL/SQL compilation warnings in the same way as with compilation errors.