Browse Prior Art Database

Dynamical Label Area

IP.com Disclosure Number: IPCOM000111703D
Original Publication Date: 1994-Mar-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 143K

Publishing Venue

IBM

Related People

Schroeder, W: AUTHOR

Abstract

Labels must be specified in jobs in the VSE/ESA operating system to describe the characteristics of the files used. They are defined via Job Control Language (JCL) commands (// DLBL and // EXTENT), and they are stored into the so-called label areas. The label area is a file on the disk specified during IPL that allows the retrieval of label information whenever a file is OPENed. The label area is divided into different label sub-areas that are partly for general use and partly belong to the different partitions within the operating system. With the development of virtual disks in VSE/ESA, the label information may be placed on virtual disks. This improves the access time to the label information since the virtual disks reside in data spaces within the virtual memory of the computer.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 42% of the total text.

Dynamical Label Area

      Labels must be specified in jobs in the VSE/ESA operating
system to describe the characteristics of the files used.  They are
defined via Job Control Language (JCL) commands (// DLBL and //
EXTENT), and they are stored into the so-called label areas.  The
label area is a file on the disk specified during IPL that allows the
retrieval of label information whenever a file is OPENed.  The label
area is divided into different label sub-areas that are partly for
general use and partly belong to the different partitions within the
operating system.  With the development of virtual disks in VSE/ESA,
the label information may be placed on virtual disks.  This improves
the access time to the label information since the virtual disks
reside in data spaces within the virtual memory of the computer.

      The creation of the label area on the virtual disk is carried
out by using the command VDISK.  A parameter 'USAGE=DLA' is employed
so that the virtual disk defined during the execution of the VDISK
command can be used to serve as new (temporary) label area.  After
execution of the VDISK command, which will only be allowed in the BG
partition before any other partition is started, all storing and
retrieving of labels will be done in this newly defined virtual disk,
and thus all labels will reside in virtual storage.  Because of the
nature of a virtual disk, the new label area is only usable until the
next IPL.  The "prior art" solution is still used to create the
permanent label area.

      In addition to the label area created on the virtual disk, the
existing label area is retained for two reasons.  Firstly, customers
with few I/O activities might want to continue to use the older
method.  Secondly, the label information for the system library in
the case of a secured sytem is needed during IPL, before Job Control
is started, and it is only possible to create a virtual disk after
Job Control has been started.

      In the prior-art solution, when the label area is created
during IPL, then a FORMAT1 label is written onto the VTOC of the disk
on which the label area is to reside in order to reserve this portion
of disk storage.  The disk start and end address and the channel and
unit address (CUU) are stored in a control block of the module
IJBSLA, which is then called, this module being the only module that
owns and controls the label information.

      In creating a label area in a virtual disk, a similar procedure
will be carried out.  In addition to the VOLUME1 record and the VTOC
which are created directly in the data space during execution of the
VDISK command, a FORMAT1 label for the label area will be moved into
the VTOC.  The use of the FORMAT1 label turns the label area into an
unexpired secured file which cannot be overwritten by another file
later during execution of user programs.  In addition, the
information about start address, end address and CUU in the
IJBSLA-control blo...