The online documentation is here:

• https://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=GREST

There is some training in the InterSystems Learning portal (you'll need to enrol/login):

• https://learning.intersystems.com/course/view.php?id=283

e.g.

• Academy: Implementing RESTful Applications - https://learning.intersystems.com/course/view.php?id=83
• Setting Up RESTful Services - https://learning.intersystems.com/course/view.php?id=776

You need to kill the pars parameter array and recreate it each time you use it. This is mentioned in the documentation:

https://docs.intersystems.com/csp/docbook/DocBook.UI.Page.cls?KEY=ESQL_parameter_overview

Important:

If you execute multiple queries that use the parameter array, kill and recreate the parameter array before each query.