Saturday, 22 October 2016

Important Database Terminology Part-1

Database-A database is a collection of information that is organized so that it can easily be accessed, managed, and updated. In one view, databases can be classified according to types of content: bibliographic, full-text, numeric, and images.
Table-This is the structure defined to store data under it. It is also called as an ENTITY.

Fields-It is also known as attributes in database terminology. It defines the property of an entity. In other words it is called as column in a table. 
For example if we have a company where employee details and department details are gathered. Employee details like empname, age, address and so on each of which form attribute is stored under structure called as EMP table Similarly department details like department name, manager and so on each of which denote field are stored in a structure called d DEPT table. Relational Database is nothing but organizing data in tabular form by creating structures as above.

ACID – The acronym standing for the properties maintained by standard database management systems, standing for Atomicity,ConsistencyIsolation, and Durability.
  • Atomicity − This property states that a transaction must be treated as an atomic unit, that is, either all of its operations are executed or none. There must be no state in a database where a transaction is left partially completed. States should be defined either before the execution of the transaction or after the execution/abortion/failure of the transaction.
  • Consistency − The database must remain in a consistent state after any transaction. No transaction should have any adverse effect on the data residing in the database. If the database was in a consistent state before the execution of a transaction, it must remain consistent after the execution of the transaction as well.
  • Durability − The database should be durable enough to hold all its latest updates even if the system fails or restarts. If a transaction updates a chunk of data in a database and commits, then the database will hold the modified data. If a transaction commits but the system fails before the data could be written on to the disk, then that data will be updated once the system springs back into action.
  • Isolation − In a database system where more than one transaction are being executed simultaneously and in parallel, the property of isolation states that all the transactions will be carried out and executed as if it is the only transaction in the system. No transaction will affect the existence of any other transaction.
Application Server – An application server that processes application-specific database operations made from application client programs. The DBMS is in-process with the application code for very fast internal access.

BLOB – An abbreviation for Binary Large OBject. In SQL BLOB can be a general term for any data of type long varbinarylong varchar, or long wvarchar. It is also a specific term (and synonym) for data of type long varbinary.

Deadlock – A situation in which resources (i.e. locks) are held by two or more connections that are each needed by the other connections so that they are stuck in an infinite wait loop. For example, connection 1 has a lock on table1 and is requesting a lock on table2 that is currently held by connection 2 which is also requesting a lock on table1. There are programming practices that can be used that will prevent deadlocks from ever occurring.

Deterministic – An attribute of a section of code whereby the limit on the time required to execute the code is known, or determined, ahead of time. This is commonly associated with real-time software.

Distributed Database – A database in which its data is distributed among multiple computers or devices (nodes) allowing multiple computers to simultaneously access data residing on separate nodes. The Internet of Things (IoT) is frequently considered a vast grid of data collection devices, requiring distributed database functionality to manage.

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