File Management - IBM

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Chapter 3. Using overrides
Overrides: An overview
These topics explain how to use overrides on AS/400:
“Overrides: An overview”provides an overview of overides on AS/400.
“Benefits of using overrides” on page 34 provides information about the types of
situations where overrides can be especially useful.
“Summary of the override commands” on page 34 provides a list of the commands
that you can use to work with overrides.
“Effect of overrides on some commands” on page 35 provides information about
how the override commands interact with other system functions.
“Using overrides in multithreaded jobs” on page 37 lists restrictions for using
overrides in multithreaded jobs.
An override is a CL command that temporarily changes a file name, a device
name, or remote location name associated with the file, or some of the other
attributes of a file. You can enter override commands interactively from a display
station or submit them as part of a batch job. You can include them in a control
language (CL) program, or issue them from other programs by calling the program
QCMDEXC. Regardless of how they are issued, overrides remain in effect only for
the job, program, or display station session in which they are issued. Furthermore,
they have no effect on other jobs that may be running at the same time.
When you create an application program, the file names specified in the program
associate files with it. The system lets you override these file names or the
attributes of the specified file when you compile a program or run a program.
You can use overrides to change most, but not all, of the file attributes that are
specified when the file is created. In some cases, you can specify attributes in
overrides that are not part of the original file definition. Refer to the command
descriptions in the CL Reference for details.
Overriding a file is different from changing a file in that an override does not
permanently change the attributes of a file. For example, if you override the
number of copies for a printer file by requesting six copies instead of two, the file
description for the printer file still specifies two copies, but six copies are printed.
The system uses the file override command to determine which file to open and
what its file attributes are.
How you work with overrides:
The system supplies three override functions:
v “Applying overrides” on page 37
v “Deleting overrides” on page 54
v “Displaying overrides” on page 57
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