Extended stored procedures are implemented by an Open Server application called XP Server, which runs on the same machine as SAP ASE. SAP ASE and XP Server communicate through remote procedure calls (RPCs).
Running ESPs in a separate process prevents SAP ASE being affected by failures that may result from faulty ESP code. The advantage of using ESPs over RPCs is that the ESP runs in SAP ASE the same way a stored procedure runs; you do not need to have Open Server to run the ESP.
XP Server is automatically installed with SAP ASE. However, if you intend to develop XP Server libraries, you must purchase an Open Server license. Everything you need to use XP Server DLLs and run XP Server commands is included with your SAP ASE license.
XP Server must be running for SAP ASE to execute an ESP. SAP ASE starts XP Server the first time an ESP is invoked and shuts down XP Server when SAP ASE exits.
On Windows, if the start mail session configuration parameter is set to 1, XP Server automatically starts when SAP ASE starts.
Normally, there is no reason for a user to start XP Server manually, since SAP ASE starts it when it receives the first ESP request of the session. However, if you are creating and debugging your own ESPs, you may find it necessary to manually start XP Server from the command line using the xpserver utility.
See the Utility Guide for the syntax of xpserver.