Browse Prior Art Database

Improved Storage Accounting Recovery

IP.com Disclosure Number: IPCOM000121974D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 181K

Publishing Venue

IBM

Related People

Kirkman, KR: AUTHOR

Abstract

A method for recovering the storage accounting information following an abnormal system termination is disclosed. The overall objective is to perform any necessary recovery on an individual object basis as objects are referenced for the first time following the abnormal termination. This technique avoids both a long recovery time while the system is being IPLed, and the run-time overhead of a commitment mechanism which would otherwise be needed to keep the accounting information accurate.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 34% of the total text.

Improved Storage Accounting Recovery

      A method for recovering the storage accounting
information following an abnormal system termination is disclosed.
The overall objective is to perform any necessary recovery on an
individual object basis as objects are referenced for the first time
following the abnormal termination.  This technique avoids both a
long recovery time while the system is being IPLed, and the run-time
overhead of a commitment mechanism which would otherwise be needed to
keep the accounting information accurate.

      The size of an object and the amount of storage used by all
objects which are owned by a user profile are externally visible in
the system.  In order to make this information readily available, it
is dynamically maintained in each object and user profile (as opposed
to being calculated each time it is needed).  In order to not burden
the system with the job of maintaining it on a persistent basis, the
information is volatile by design and can, therefore, be lost on an
abnormal termination.  Subsequently, this information is considered
"suspicious" until it can be verified/corrected on the next
reference.

      The following key elements are described in this invention:
-  The technique for making all size information for objects and user
profiles appear "suspicious" following an abnormal termination.
-  The technique for verifying/correcting the size of a "suspicious"
object when the object is first referenced.
-  The technique for verifying/correcting the amount of storage used
by objects owned by a "suspicious" user profile.
   (Since this potentially involves looking at each owned object and
may, therefore, be long-running, this recovery may not necessarily be
performed on the first reference to the user profile. Rather, it may
be advantageous to perform it in conjunction with other operations on
the user profile which reference all owned objects anyway.  In that
case, the amount of storage owned by the user profile may be regarded
as an approximation until the operation with which the recovery is
associated has been performed.)
      Following are the constructs involved in the invention:

      SYSIPL:  This is a persistent system-wide field containing the
number of times the system has been IPLed. When the system is
running, a program referencing this field can think of it as
containing the most recent IPL number.

      SYSVFYIPL:  This is a persistent system-wide field containing
the IPL number immediately following the most recent abnormal
termination.

      OBJVFYIPL:  This is a persistent field maintained in each
object.  It contains a copy of the value of SYSIPL that was current
the last time the object's size was verified/corrected.

      OBJSIZE:  This is a persistent field maintained in each object.
It contains the object's size.  It is established when the object is
created and is incremented or decremented as the verified/corrected
object...