Browse Prior Art Database

Multiple Levels of Serialization for Backing Up Open Data Sets

IP.com Disclosure Number: IPCOM000112651D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 116K

Publishing Venue

IBM

Related People

Hofmeister, JP: AUTHOR [+2]

Abstract

A method using multiple levels of serialization to backup a data set that is open for update. The multiple levels of serialization ensures that data integrity and security are maintained.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Multiple Levels of Serialization for Backing Up Open Data Sets

      A method using multiple levels of serialization to backup a
data set that is open for update.  The multiple levels of
serialization ensures that data integrity and security are
maintained.

      This discloses using multiple levels of serialization to backup
data sets that are open for update, and at the same time, ensure the
following:  Any update activity to the data set is detected, and
recovery actions are disallowed while the data set is being backed
up.  The levels of serialization are:

o   A Backup-While-Open status (BWO status) to signal that the data
    set can be backed up while it is open for update.  This permits
    serialization between a program that controls the data set and
    the program that backs up the data set.

o   A Backup-While-Open enqueue (BWODSN) to prevent a recover program
    from replacing the data set while it is also being backed up.
    This permits serialization between the backup program and the
    recover program in case the data set control program is ended
    while the data set is in the process of being backed up.  This
    prevents deletion of the data set, with subsequent data security
    exposure, while it is being backed up.

o   A Backup-While-Open count (BWO count) that is used as a
    state-change token for the data set:  It is updated by adding one
    whenever the Backup While Open status is changed.  This permits
    serialization between the backup program and any update activity
    against the data set during the time the data set is being backed
    up.

      Referring to the block diagram, a data-base control program (1)
opens a data set (8) through access method services  (3), which
establishes a system-level enqueue (4) against the data set.  The
data-base control program then uses catalog services (5) to signal
that the data set is eligible to be backed up even though it is open
for update.  Catalog services updates the Backup-While-Open status
(6) and the Backup-While-Open Count (7) in the volume record for the
data set.

      Subsequently, a backup program (9) is started to backup the
open data set.  The backup program attempts to obtain the normal,
system-level enqueue (4) for the data set.  When this fails, the
backup program obtains the Backup-While-Open enqueue (10) for the
data set; then uses catalog services to obtain the Backup-While-Open
status and count; and starts the backup of the open data set.

      While the data set is being backed up, the data-base control
program program may end and a recover program (11) may be started.
Because the data-base control program program is ended, the recover
program is able to obtain the system-level enqueue for the data set,
but not the Backup-While-Open enqueue.  Because the recover program
is unable to obtain bo...