The migrationofthis two databases may lead to damage the system design. In the real system, application interface by relational database with the help of SQL. At same period of time to use both the databases the application design need to be changed. At the time of integratingreal system to NoSQL database, a mechanism is to be needed for datamigration from relational to NoSQL. Relational database is the most widely used data storage technology for many years.
In today’s world requirement for data processing have prompted emergence of new data storage, retrieval and processing mechanism. One of such mechanism is NoSQL databases is also called non-relational databases.NoSQL databases is one of the mechanisms, and is called as non-relationaldatabases. Numerous companies sift to NoSQLdatabase and utilize it for storing and managing data andrelational database system must be migrated to NoSQL. Due tothedifference in the schema of NoSQL database and relationaldatabases, user have to learn a new database.
As the join operationis not supported in the NoSQL, user have to collectthedata fromdifferent table and leads to a poor performance. So the schema conversion is must for the migration to relational to NoSQL. Designed NoSQL is termed as ‘Not Only SQL’ for distributed data store. To overcome the limitations of RDBMSs in storing and processing cloud big data, NoSQL databaseshave been developed for large scale and high concurrencyapplications. Web 2.0 applications needs large data storage withflexible schema for attributes such as picture, video, text, comments, and other information,theNoSQL databases are mainly designed to comply with the requirements of Web 2.0applications.
Key features of NoSQLdatabasesincludes: 1.Ability to scale horizontally. 2. Ability to partition or distribute over many functions 3. Comparably weaker concurrencythan ACID. 4.
Compared to SQL binding, simple call level protocol.5. Ability to attach newfeature to datarecords dynamically.
6. Capable use of RAM and distributed indexes for data storage. Horizontal scaling, replication and distribution of data overvarious purpose make data reading and writing operationsbecomesfaster. ACID properties which are essential for dataconsistency for the parallel transaction, but NoSQL does notoffer the ACID properties. In the distributed environmentthemain requirement is system scalability. The web basedapplications mainly run on such distributed environment.
Andfor a distributed systemit is not possible to ensure simultaneous Consistency, Availability and Partition tolerance at the same which is stated as the CAP theorem that articulates two of them can be achieved. A weaker model BASE (BasicallyAvailable, Soft state, Eventual consistency)replaces ACID inorder to keep NoSQL data consistent and reliable. Invented by Eric Brewer and according to BASE propertiesaredescribed as: Basic availability: Any request will be responded with successfulor failed execution. Soft state: The state of thesystem is ‘soft’ which may change over time. So due to eventual consistencychanges even may be going on without any input.
Eventual consistency: Eventually the database will beconsistent even though it could be inconsistent momentarily. Five categories of NoSQL databases are: column-oriented,Document –oriented, key-value, graph, multi-model. The mostimportant types of databases for some years is key-valuestore and documentdatabases. In proposed model we concentrateNoSQL database as document-oriented database.