File Management - IBM

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Sharing files
12 File Management V4R5
v *ALL. All users that do not have specific user or group authority to the file have
all data authorities and all object authorities.
v Authorization list name. An authorization list is a list of users and their
authorities. The list allows users and their different authorities to be grouped
together.
Specifying or changing authorities on existing files:
To specify or change public authority on an existing file, use the Edit Object
Authority (EDTOBJAUT), Grant Object Authority (GRTOBJAUT), or Revoke Object
Authority (RVKOBJAUT) commands to grant or revoke the public authority of a
file.
For more information about using the security function on the system, see the
Security - Reference or the Tips and Tools for Securing Your AS/400, SC41-5300-04.
AS/400 file management provides several levels of support for shared files. The
system automatically provides the first level of support. By default, the system lets
many users and more than one job use one file at the same time. The system
allocates the file and its associated resources for each use of the file in such a way
that it can prevent conflicting uses. Within the same job, programs can share files if
one program opens the same file more than once or if different programs open the
same file. Even though the same file is being used, each open operation creates a
new path from the program to the data or device, so that each open represents an
independent use of the file.
Open data path
A closer level of sharing within a job allows more than one program to share the
same path to the data or device. This path, called an open data path, is the path
through which all of the read and write operations for the file are performed. You
can use this level of sharing by specifying the SHARE parameter on the create file,
change file, and override file commands. The SHARE parameter allows more than
one program to share the file status, positions, and storage area. It can improve
performance by reducing the amount of main storage the job needs and by
reducing the time it takes to open and close the file. AS/400 bases this level of
sharing on two models:
v
The original program model is the set of functions for compiling source code
and creating high-level language programs on the AS/400 system before the
Integrated Language Environment (ILE) model was introduced.
v The ILE model is the set of constructs and interfaces that provide a common
run-time environment and run-time bindable application program interfaces
(APIs) for all ILE-conforming high-level languages.
Shared files in the original program model
In the original program model, the SHARE(*YES) parameter lets two or more
programs that run in the same job share an open data path (ODP). It connects the
program to a file. If not specified otherwise, every time a file is opened a new
open data path is built. You can specify that if a file is opened more than once and
an open data path is still active for it in the same job, the active ODP for the file