Browse Prior Art Database

Certification With Adaptive Time Selection

IP.com Disclosure Number: IPCOM000099220D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 75K

Publishing Venue

IBM

Related People

Dias, DM: AUTHOR [+2]

Abstract

A concurrency control method is described that can reduce the number of transactions aborted due read-write conflicts in a database transaction processing by using (limited) history information. For many there are usually many more reads than writes, therefore a large fraction of the data contention among are of the read-write type. In certification (optimistic) concurrency control, such conflicts lead transaction aborts. By using the proposed method, better performance can be obtained due to reductions in the frequency of aborts.

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Certification With Adaptive Time Selection

       A concurrency control method is described that can reduce
the number of transactions aborted due read-write conflicts in a
database transaction processing by using (limited) history
information.  For many there are usually many more reads than writes,
therefore a large fraction of the data contention among are of the
read-write type.  In certification (optimistic) concurrency control,
such conflicts lead transaction aborts.  By using the proposed
method, better performance can be obtained due to reductions in the
frequency of aborts.

      In this method, each transaction obtains a unique time at
commit time.  A read time stamp (Tr) and write time (Tw) for each
data item is maintained.  The read time is the time stamp of the
youngest (i.e. latest in committed transaction which read the data.
The write stamp is the time stamp of the youngest committed which
updated the data.  Also maintained are history time stamps
(T1w,...,Tkw) for the data, with as the oldest update and Tkw as the
latest update, so Tw=Tkw, that is, the time stamp of the last k
updating the data time.  A transaction views data item as a (name,
version) pair.  For each data read, the Tw of the data is tracked and
this Tw is as its version.  Before certification, a time stamp is
generated for the transaction.  For each data item Dri i=1,...,m, the
version read is checked with the Tw of the data item.  If all match,
the transaction certified.  The read and write time stamps and th...