Executable Server Page (ESP) directives are directives that allow the building of dynamic pages at the server rather than having only dynamic HTML to control the web page construction. The main benefit of ESP directives is that they allow you to tie the data and the visual elements (such as HTML, text, JavaScript, and images) on the page together without embedding these elements into your programs. The programs only need to retrieve data.
ESP directives are coded into a WebCenter web page so that the web page can interact with CA Mainframe Network Management products. The web page must be named with the .esp suffix. ESP directives enable your web page to call an NCL procedure and share variables back into your web page. ESP includes three directive types with any other data (such as HTML and JavaScript) interspersed in between. All directives begin with the directive start delimiter <% and end with the directive end delimiter %>.