Objectivity/DB: Difference between revisions

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Objects can be linked to other objects using named uni-directional or bi-directional links. The links can have a [[cardinality]] of 1:1, 1:many, many:1 or many:many and use the OIDs to speed up the navigation of networks of objects.<ref name="bloor">{{cite web|url=http://www.bloorresearch.com/analysis/objectivity-infinitegraph/|title=Objectivity and InfiniteGraph|author=Philip Howard|date=May 29, 2012|publisher=Bloor|accessdate=December 1, 2014}}</ref> The OIDs are also used in support of scalable collections (tree, list, set etc.), indices and [[hash table]]s. Eliminating the relational [[Join (SQL)|Join]] operations inherent in a relational database gives Objectivity/DB a performance advantage.<ref>{{cite book|author1=Suzanne W. Dietrich|author2=Susan D. Urban|year=2011|title=Fundamentals of Object Databases|publisher=Morgan & Claypool Publishers|page=2|isbn=9781608454761|url=https://books.google.com/books?id=x_8myOrO1dgC&q=Fundamentals+of+Object+Databases|accessdate=December 3, 2014}}</ref><ref>{{cite book|editor1=Alan Dearle|editor2=Roberto V. Zicari|year=2010|title=Objects and Databases, Third International Conference Proceedings, ICOODB|publisher=Springer|page=34|isbn=978-3642160912|url=https://books.google.com/books?id=AHHE015TBrIC|accessdate=December 3, 2014}}</ref><ref>{{cite book|author=C.S.R Prabhu|year=2011|title=Object-Oriented Database Systems - Approaches and Architecture, Third Edition|publisher=Asoke K. Ghosh, PHI Learning Private Limited|page=67|isbn=9788120340930|url=https://books.google.com/books?id=aRdl1j31MfoC|accessdate=December 3, 2014}}</ref>

Objectivity/DB is also differentdiffers from [[RDBMS]]s in the way in whichhow it handles queries. The application declares and initializes an iterator that locates and returns qualified objects as soon as they are locatedfound. The Objectivity/DB Parallel Query Engine splitsdivides queries into subtasks directedaimed at individual databases or containers. Remote query agents servicehandle each subtask and returnsend results back to the iterator. The Parallel Query Engine hasconsists of two replaceable components: a splitter that candetermines determinethe howbest toway bestto subdividedivide the task and a filter in the query agent that can further refinerefines a query. AFor example, a query involvingregarding cities in Europe mightcould be splitdivided into forty -nine subtasks, oneeach for eacha different country. The filter mightmay access an external data source beforeto qualifyingqualify or disqualifyingdisqualify the objects thatfound by the Query Agent has found in the Objectivity/DB database or container.

Databases and system data (catalogs and [[Database schema|schema]]) can be replicated to multiple locations using a quorum based synchronous replication mechanism. Replicas that are temporarily separated from the quorum are transparently resynchronized when they are reconnected to the network that services them and their peers. Individual databases and lock servers can be allocated votes that are used to determine whether or not a client can update a replica.