Site Recovery in Replicated Distributed Database Systems.
Bharat Bhargava, Zuwang Ruan · Purdue e-Pubs (Purdue University System) · 1986
A solution to the problem of integrating a recovering site inLo a distributed database system is presented. The basic idea used for the correct recovery is to maintain a consistent view of the status (up or down) of all sites. This view need not be the exact current status of the sites. but is the status as perceived by other sites. The session number is used to represent the actual state of a site. while the nominal session number is used for the session number as perceived by other sites. The consistent view of the nominal session numbers are maintained by control transactions. which run concurrently with user transactions. This approach provides a high degree of availability. A data item is available to a transaction as long as one of its copies is in an operational site and the transaction knows lhe site's session number. The recovery procedure allows the recovering site to resume its normal operations as soon as possible.