IBM AS/400 manual Processing an Externally Described WORKSTN File, Using Subfiles

Using Externally Described WORKSTN Files

Processing an Externally Described WORKSTN File

When an externally-described WORKSTN file is processed, the OS/400 sys transforms data from the program to the format specified for the f the data. When data is passed to the program, the data is transf format used by the program.

The OS/400 system provides device-control information for processing input

operations for the device. When an input				record is	requested from
OS/400 system issues the request,			and then removes device-control infor
from the data before passing the			data to the program. In additio
system can	pass	indicators to the	program	indicating	which fields, or
the record	have	been changed.

When the program requests an output operation, it passes the output OS/400 system. The OS/400 system provides the necessary device-control mation to display the record. It also adds any constant information record format when the record is displayed.

When

a

record

is passed to a program,

the fields are arranged in

they

are specified

in

the

DDS.

The

order

in which

the

fields are

on the

display

positions

(line

numbers

and

position) assigned to the f

DDS. The order in which the fields

are

specified

in the

DDS and t

they

appear on

the

screen need

not

be

the

same.

For more information on processing WORKSTN files, see “Valid WORKSTN File Operations” on page 341.

Using Subfiles

Subfiles can be specified in the DDS for a display-device file to multiple records of the same type on the display. (See Figure 166 o subfile is a group of records that is read from or written to a example, a program reads records from a database file and creates output records. When the entire subfile has been written, the prog entire subfile to the display device in one write operation. The w change data or enter additional data in the subfile. The program t entire subfile from the display device into the program and process in the subfile individually.

Records

that you want

to be included in a subfile are

specified

file.

The number

of

records that can

be

included

in a

subfile must

in

the

DDS.

One

file

can

contain

more

than

one subfile,

and

up

to

1

be

active

concurrently.

Two subfiles can be displayed

at

the

same

The DDS for a subfile

consists of two record formats:

a

subfile-rec

subfile control-record format. The subfile-record format

contains

the

that

is

transferred

to

or

from

the

display file

under

control

of

t

record		format. The		subfile control-record format causes the physical
control	operations		of	a	subfile	to	take	place.	Figure 167	on page 337
example		of the	DDS	for	a subfile-record			format,	and Figure 168 on pa
shows	an	example	of	the	DDS for	a	subfile control-record			format.

For a description of how to use subfileDDSkeywords,Reference.s e the

Chapter 18. Using WORKSTN Files335