The following example shows the use of a file override at compilation time.
Assume that you want to use an externally described file for a TAPE device
which does not have field-level description. You must:
Define a physical file named FMT1 with one record format that contains
the description of each field in the record format. The record format is defined
on the data description specifications (DDS). For a tape device, the externally
described file should contain only one record format.
Create the file named FMT1 with a Create Physical File CL command.
Specify the file name of QTAPE (which is the IBM-supplied device file
name for magnetic tape devices) in the RPG program. This identifies the file
as externally described (indicated by an E in position 22 of the file description
specifications), and specifies the device name SEQ in positions 36 through
42.
Use an override command–OVRDBF FILE(QTAPE) TOFILE(FMT1)–at
compilation time to override the QTAPE file name and use the FMT1 file name.
This command causes the compiler to copy in the external description of the
FMT1 file, which describes the record format to the RPG compiler.
Create the RPG program using the CRTBNDRPG command or the CRTPGM command.
Call the program at run time. The override to file FMT1 should not be
in effect while the program is running. If the override is in effect, use
the CL command DLTOVR (Delete Override) before calling the program.
Note:
You may need to use the CL command OVRTAPF before you call the program
to provide information necessary for opening the tape file.
Figure 164. Redirecting File Input and Output Example
