External Procedures Overview

External procedures are functions written in a third-generation language (C, for example) and callable from within PL/SQL or SQL as if they were a PL/SQL routine or function.

External procedures let you take advantage of strengths and capabilities of a third-generation programming language in a PL/SQL environment.

Note:

Oracle Database also provides a special purpose interface, the call specification, that lets you call external procedures from other languages, as long as they are callable by C.

The main advantages of external procedures are:

Performance, because some tasks are performed more efficiently in a third-generation language than in PL/SQL, which is better suited for SQL transaction processing
Code re-usability, because dynamic link libraries (DLLs) can be called directly from PL/SQL programs on the server or in client tools

You can use external procedures to perform specific processes:

Solving scientific and engineering problems
Analyzing data
Controlling real-time devices and processes

Note:

Special security precautions are warranted when configuring a listener to handle external procedures.

To create and use an external procedure, perform the following steps:

Note:

You must have a C compiler and linker installed on your system to build DLLs.
You can combine the instructions described in the fourth and fifth tasks into one SQL script that automates the task of registering and executing your external procedure. See ORACLE_HOME\rdbms\extproc\extern.sql for an example of a SQL script that combines these steps.