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Retaining a Moving Write Lock for Better Interactive Performance

IP.com Disclosure Number: IPCOM000103979D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 49K

Publishing Venue

IBM

Related People

Madduri, HH: AUTHOR

Abstract

The use of a moving write lock is used for managing updates to a replicated in-memory data object. The replica control algorithm is a variant of the standard master-copy (or primary-copy) algorithm where the master copy is updated first and the changes are propagated to all shadows. The variation is that any shadow copy can update itself first and then forward its updates to the master copy, provided it obtains a write lock from the master prior to the update and holds it during the update. At any time, there is only one copy that is authorized to "write" the data object. In this sense, the write lock moves among the copies. In terms of update capability, the master copy is like all others copies, except that it holds the lock when no one else needs the lock and it also broadcasts the updates to all.

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Retaining a Moving Write Lock for Better Interactive Performance

      The use of a moving write lock is used for managing updates to
a replicated in-memory data object.  The replica control algorithm is
a variant of the standard master-copy (or primary-copy) algorithm
where the master copy is updated first and the changes are propagated
to all shadows.  The variation is that any shadow copy can update
itself first and then forward its updates to the master copy,
provided it obtains a write lock from the master prior to the update
and holds it during the update.  At any time, there is only one copy
that is authorized to "write" the data object.  In this sense, the
write lock moves among the copies.  In terms of update capability,
the master copy is like all others copies, except that it holds the
lock when no one else needs the lock and it also broadcasts the
updates to all.  This kind of scheme is attractive when the shadow
copies drive visual displays at their respective sites, since the
user does not have to wait for visual feedback until the master is
updated.
     The current invention suggests retaining the moving write lock
at a shadow until someone else asks for it.  This results in better
performance in cases where updates occur in bursts and the lock
movement from shadow to shadow is slow.  For a given shadow, the
overhead of going to the master and getting a lock is incurred only
once per burst of updates, instead of once per update.
     The...