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Database Files: Physical Files: A Physical File Is A File That Actually Contains Data Records. This

The document summarizes four categories of files in the AS/400 system: database files which allow permanent storage of information and can be accessed by multiple programs, device files which control data transfer between physical devices and programs, DDM files which allow accessing data on remote systems, and save files which store program objects. Database files include physical files which contain actual data records and logical files which define access paths to data in physical files.

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168 views1 page

Database Files: Physical Files: A Physical File Is A File That Actually Contains Data Records. This

The document summarizes four categories of files in the AS/400 system: database files which allow permanent storage of information and can be accessed by multiple programs, device files which control data transfer between physical devices and programs, DDM files which allow accessing data on remote systems, and save files which store program objects. Database files include physical files which contain actual data records and logical files which define access paths to data in physical files.

Uploaded by

Vivian
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOC, PDF, TXT or read online on Scribd
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The AS/400 system has four categories of files: database files, device files, DDM

files, and save files.

Database Files
Database files allow information to be permanently stored on the system. Multiple
programs can access this information in different ways.
A database file is subdivided into groups of records called members.
There are two types of database files: physical files and logical files.
Physical Files: A physical file is a file that actually contains data records. This
makes physical files similar to disk files on other systems. A physical file can
contain only fixed-length records, all of which have the same format.
Logical Files: A logical file is a database file through which data from one or
more physical files can be accessed. The format and organization of this data is
different from that of the data in the physical file(s). Each logical file can define a
different access path (index) for the data in the physical file(s). Each logical file
can exclude and reorder the fields defined in the physical file(s).

Device Files
A device file reads from or writes to a device or remote system. A device file controls
the transfer of data between the physical device or remote system and the
program.

DDM Files
Distributed Data Management (DDM) allows you to access data that reside on
remote systems that support DDM. DDM files are supported by the COBOL compiler.
You can retrieve, add, update, or delete data records in a file that resides on
another system.
When you compile a source program that is on a remote system, the COBOL/400
compiler expects a source type of CBL. If the source type is not CBL, the compiler
issues a message indicating that it encountered an unexpected source member
type. To resolve this discrepancy, you should recompile the program in the environment
indicated by the source member type, or change the source member type,
or use the correct compiler indicated by the source member type.

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