File Management - IBM

COPIES(2)
From Override 2
LPI(4) From Override 4
Because no specific override is found for PRT2 in program B, override 4 is applied.
In program A, override 2 specifies PRT2 and is applied.
When program X opens the file PRT3, the opened file has the following attributes:
COPIES(1)
From Override 1
LPI(8) From Override 5
In program B, override 5 specifies PRT3 and is applied. Because no specific
override is found for PRT3 in program A, override 1 is applied.
When program X opens the file PRT4, the opened file has the following attributes:
COPIES(2)
From Override 3
LPI(8) From Override 6
In program B, override 6 specifies PRT4 and is applied. In program A, override 3
specifies PRT4 and is applied.
Applying overrides when compiling a program
Overrides may be applied at the time a program is being compiled for either of
two purposes:
v To select the source file
v To provide external data definitions for the compiler to use in defining the
record formats to be used on I/O operations
Overrides to the source file are handled just like any other override. They may
select another file, another member of a database file, another label for diskette or
tape, or change other file attributes.
You can also apply overrides to files that are used within the program being
compiled, if they are being used as externally described files in the program. These
files are not opened at compile time, and thus the overrides are not applied in the
normal manner. These overrides are used at compile time only to determine the
file name and library that will be used to define the record formats and fields for
the program to use I/O operations. Any other file attributes specified on the
override are ignored at compile time. It is necessary that these file overrides be
active at compile time only if the file name specified in the source for the program
is not the file name that contains the record formats that the application needs.
The file name that is opened when the compiled program is run is determined by
the file name that the program source refers to, changed by whatever overrides are
in effect at the time the program runs. The file name used at compile time is not
kept. The record formats in the file that is actually opened must be compatible
with those that were used when the program was compiled. Obviously, the easiest
way to assure that records are compatible is to have the same overrides active at
run time that were active at compile time. If your program uses externally
Chapter 3. Using overrides 53