File Management - IBM

Application 1 Application 2
Application program
Open changes
parameter P1
to QRT
Override CL command
changes parameter P2
to END
P1 = QRT
P2 = END
P3 = 30
.
.
.
File
.
.
.
P1 = RPT
P2 = NEXT
P3 = 30
.
.
.
Open changes
parameter P3
to 10
Opened file Opened file
Figure 2. Temporarily Changing a File
20 File Management V4R5
Application program
Override CL command
changes parameter P2
to IMD
P1 = RPT
P2 = IMD
P3 = 10
.
.
.
Once an application establishes a connection between itself and the file by opening
the file, it can then proceed to use the file for either input or output operations. In
the case of a database file, the open process establishes a path between the
application and the actual database file. For device files, a path is established
between the application and the actual device, or to a spooled file if the spooling
attribute is active for the device file. In all cases, the application connects to what it
wants to use, and those connections determine what input or output operations are
valid. Not all operations are valid with all file types. The application must be
aware of what file types it uses and then use only those operations which are valid
for those types.
Open considerations when using *LIBL with a DDM file
RSLH196-1
Take note of the following considerations when you open DDM files and specify
*LIBL for the library:
v The system first searches the library list for a local database file with the
specified member. Even if the local database file is located in a library later in
your library list than the library containing the DDM file, the local database file
containing the specified member is used.