HP RPG/XL Programmer's Guide (30318-90001)

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Chapter 3 Using Disc Files in an RPG Program

RPG contains language elements that let you process several kinds of disc

files. You can use MPE files, Keyed Sequential Access Method (KSAM)

files and TurboIMAGE databases. The following list summarizes these

files and how you can use them in RPG programs:

File type: Ways you can access the file:

MPE Sequentially, randomly.

KSAM Sequentially, sequentially within key limits,

randomly and chronologically.

TurboIMAGE Sequentially, sequentially within key limits,

randomly.

A KSAM file consists of a data file and a key file. Data files contain

the actual data records and are maintained in chronological sequence

(records are placed in the file in the order that they are added). The

key file lets you access the data file records in key sequence. When you

create a KSAM file, you specify the fields that are the keys.

A TurboIMAGE database is a collection of files (data sets) whose data

field relationships are maintained automatically. You can easily query

data in TurboIMAGE databases and there are extensive file security

provisions that you can use.

This chapter discusses KSAM files and TurboIMAGE databases and how you

access and use them in RPG programs.

Indexed Disc Files (KSAM)

The following list summarizes the advantages and disadvantages of using

KSAM files. For in-depth information on KSAM files, see the

KSAM/3000

Reference Manual

Advantages:

* Can access records sequentially, chronologically, and by partial or

generic key value

* Efficient disc usage; the data portion of the file grows as records

are added

* No special utilities are required for loading and unloading data

* Multiple keys

* Key fields can be updated

* Deleted records are retrievable

* Duplicate keys

* KSAM files can be processed by FCOPY, SORT, EDITOR; you can also use

the operating system FILE command with them

* Fast updating when processing data sequentially

* RPG Specifications are easy to code

* Fixed or variable length data records

Disadvantages:

* No query facilities