IBM AS/400 manual Creating a Service Program, Service Program Overview

Service Program Overview

Chapter 8. Creating a Service Program

This chapter provides:

¹ An overview of the service program concept

¹ Strategies for creating service programs

¹ A brief description of the CRTSRVPGM command

¹An example of a service program

Service Program Overview

A service program is a bound program (type *SRVPGM) consisting of a s cedures that can be called by procedures in other bound programs.

Service programs are typically used for common functions that are fre within an application and across applications. For example, the ILE com service programs to provide run-time services such as math functions a input/output routines. Service programs enable reuse, simplify maintenanc reduce storage requirements.

A	service program			differs	from	a	program in two ways:
¹	It	does	not	contain a	program		entry procedure. This means that y
	a	service	program using		the	CALL	operation.

¹A service program is bound into a program or other service progra binding by reference.

When you bind a service program to a program, the contents of the program are not copied into the bound program. Instead, linkage infor service program is bound into the program. This is called 'binding by contrast to the static binding process used to bind modules into pro

Because a service program is bound by reference to a program, you service program's exported procedures using bound procedure calls. The has a certain amount of overhead because the binding is not complet service program is called. However, subsequent calls to any of its faster than program calls.

The set of exports contained in a service program are								the	interf
provided	by	it.	You	can use	the Display	Service	Program	(DSPSRVPGM) c
or the service program listing					to see what variable and procedure n
able for	use	by	the	calling	procedures.	To see	the exports		associ

program PAYROLL, you would enter:

DSPSRVPGM PAYROLL DETAIL(*PROCEXP *DATAEXP)

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