ABL returns all server-side errors to the client that occur before any remote procedure is executed. An example of this type of server-side error is where the client tries to execute a remote procedure that does not exist. Generally, both the client and application server can resume normal execution.

ABL also returns all network connection and authentication errors; for example, if an HTTP connection cannot be made, authentication cannot be established with the application server, or the application server is not configured properly.