TI Heterogeneous and Autonomous Transaction Processing 

LT CUCS-009-91 

OR COLUM 

YR 1991 

AU C. Pu 

AU A. Leff 

AU S.W.F. Chen 

AB Transaction processing (TP) systems have been evolving towards
greater distribution, heterogeneity, and autonomy.  In the
heterogeneity and autonomy dimensions, we present concrete and
independent steps in this evolution starting from solutions in
classic distributed TP.  For cooperative heterogeneous TP, we
describe the Superdatabase architecture, which provides
transaction atomicity over heterogeneous component databases. 
Superdatabase shows that if a component database supports local
recovery and concurrency control, necessary ingredients in
classic distributed TP, then it can become part of a cooperative
heterogeneous TP system.  The feasibility of superdatabase
architecture is demonstrated by the Supernova prototype
implementation in the Harmony project.  For autonomous TP
execution, we describe the asynchronous execution of transactions
for greater performance and availability.  The solution is based
on epsilon-serializability (ESR) that models temporary
inconsistency explicitly.  The database maintns serializable
consistency, but applications that can tolerate a bounded amount
of inconsistency may gain additional concurrency and
availability.  Efficient replica control and divergence control
methods make ESR-based asynchronous TP attractive.  The
similarities between these methods and traditional concurrency
control methods make them clearly feasible.  These positive steps
in the evolution towards a truly heterogeneous and autonomous TP
system are just the beginning.  We discuss some of the challenges
in both areas and in their combination.