An extended stored procedure (ESP) has the interface of a stored procedure, but instead of containing SQL statements and control-of-flow statements, it executes procedural language code that has been compiled into a dynamic link library (DLL).
The procedural language in which an ESP function is written can be any language capable of calling C language functions and manipulating C datatypes.
ESPs allow Adaptive Server to perform a task outside the RDBMS in response to an event occurring within the database. For example, you could use an ESP to send an e-mail notification or network-wide broadcast in response to an event occurring within the Relational Database Management System (RDBMS).
There are some Adaptive Server-supplied ESPs, called system extended stored procedures. One of these, xp_cmdshell, allows you to execute an operating system command from within Adaptive Server. Chapter 16, “Using Extended Stored Procedures,” describes ESPs. The Reference Manual includes detailed information about system ESPs.
ESPs are implemented by an Open Server™ application called XP Server™, which runs on the same machine as Adaptive Server. Remote execution of a stored procedure is called a remote procedure call (RPC). Adaptive Server and XP Server communicate through RPCs. XP Server is automatically installed with Adaptive Server.
