Extended stored procedures provide a way to dynamically load and execute external procedural language functions from within Adaptive Server. Each ESP is associated with a corresponding function, which is executed when the ESP is invoked from Adaptive Server.
An ESP allows Adaptive Server to perform a task outside Adaptive Server in response to an event occurring within Adaptive Server. For example, you could create an ESP function to sell a security (a task performed outside Adaptive Server). This function is invoked in response to a trigger that is fired when the price of the security reaches a certain value. Or you could create an ESP function that sends an e-mail notification or a network-wide broadcast in response to an event occurring within the relational database system.
For the purposes of ESPs, “a procedural language” is a programming language that is capable of calling a C language function and manipulating C language datatypes.
After a function has been registered in a database as an ESP, it can be invoked just like a stored procedure from isql, from a trigger, from another stored procedure, or from a client application.
ESPs can:
Take input parameters
Return a status value indicating success or failure and the reason for the failure
Return values of output parameters
Return result sets
Adaptive Server supplies some system ESPs. For example, one system ESP, xp_cmdshell, executes an operating system command from within Adaptive Server. You can also write your own ESPs using a subset of the Open Server application programming interface (API).
