What is the benefit of using Externally Described files
over Internally
Described?

Answer Posted / prima krishnan

Program Described:-

For program-described files, the file name entered in
positions 7 through 14 must also be entered on:

° Input specifications if the file is a primary, secondary,
or full procedural file

° Output specifications or an output calculation operation
line if the file is an output, update, or combined file, or
if the file is an input file and records are also being
added to the file

° Extension specifications if the file is a table, array, or
record address file, or a file processed by a record-address
file

° Calculation specifications if the file name is required
for the operation code specified

° Line counter specifications if the device is a printer and
default values are to be overridden.

Externally Described File

For externally described files, the file name entered in
positions 7 through 14 is the name used to locate the record
descriptions for the file. The following rules apply to
externally described files:

° Input and output specifications for externally described
files are optional. They are required only if you are adding
RPG/400 functions, such as control fields or record
identifying indicators, to the external description retrieved.

° When an external description is retrieved, the record
definition can be referred to by its record format name on
the input, output, or calculation specifications.

° A record format name must be a unique symbolic name.

° A logical file with two record formats of the same name
cannot have the duplicate format names renamed and cannot be
externally described. However, such a file can be accessed
if it is program described.

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