File Management - IBM

The file MSTOUT opens because of the override that is requested by the call to the
QCMDEXC program.
In an actual program, you might want to use data that is supplied by the program
as a parameter of the override. You can do this by using program variables in the
call to QCMDEXC. For more information on the use of program variables, refer to
the appropriate language information.
Securing files against overrides
On occasion, you may want to prevent the person or program that calls your
program from changing the file names or attributes you have specified. You can
prevent additional file overrides by coding the SECURE(*YES) parameter on a file
override command for each file that needs protection. This protects your file from
overrides at lower call levels, the activation group level, and the job level.
The following shows an example of a protected file:
Override 1 OVRPRTF FILE(PRINT1) SPOOL(*NO)
Override 2 OVRDBF FILE(NEWEMP) TOFILE(OLDEMP) +
MBR(N67)
CALL PGM(CHECK)
Program CHECK
Override 3 OVRDBF FILE(INPUT) +
TOFILE(NEWEMP) MBR(N77) +
SECURE(*YES)
CALL PGM(EREPORT)
Program EREPORT
(NEWEMP and PRINT1 are opened.)
Override 4 OVRDBF FILE(INPUT) +
TOFILE(NEWEMP) MBR(N77)
CALL PGM(ELIST)
Program ELIST
(OLDEMP and PRINT1 are opened.)
When the example calls program EREPORT, it attempts to open the files INPUT
and PRINT1. EREPORT actually opens file NEWEMP, member N77. Because
override 3 specifies SECURE(*YES), the system does not apply override 2. When
the example calls program ELIST, it also attempts to open the files INPUT and
PRINT1. ELIST actually opens files OLDEMP, member N67. Because override 4 has
the same name as override 3 and is at the same call level as override 3, it replaces
override 3. Thus, the file is no longer protected from overrides at lower call levels,
and the system applies override 2 for program ELIST.
PRINT1 is affected only by override 1, which is in effect for both programs
EREPORT and ELIST.
Using a generic override for printer files
The OVRPRTF command allows you to have one override for all the printer files
in your job with the same set of values. Without the generic override, you would
have to do a separate override for each of the printer files.
Chapter 3. Using overrides 51