Database Architecture




We are now in a position to provide a single picture (Figure 1.5) of the various
components of a database system and the connections among them.


The architecture of a database system is greatly influenced by the underlying
computer system on which the database system runs. Database systems can be
centralized, or client-server, where one server machine executes work on behalf
of multiple client machines. Database systems can also be designed to exploit parallel
computer architectures. Distributed databases span multiple geographically
separated machines.


The issues include how to store data, how to ensure atomicity of
transactions that execute at multiple sites, how to perform concurrency control,
and how to provide high availability in the presence of failures. Distributed query

 

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processing and directory systems are also described in this chapter.
Most users of a database system today are not present at the site of the
database system, but connect to it through a network. We can therefore differentiate
between client machines, on which remote database users work, and server
machines, on which the database system runs.

Database applications are usually partitioned into two or three parts, as in
Figure 1.6. In a two-tier architecture, the application resides at the client machine,
where it invokes database system functionality at the server machine through 
query language statements. Application program interface standards like ODBC
and JDBC are used for interaction between the client and the server.  

Database Architecture

Database Architecture

 

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In contrast, in a three-tier architecture, the client machine acts as merely a
front end and does not contain any direct database calls. Instead, the client end
communicates with an application server, usually through a forms interface.
The application server in turn communicates with a database system to access
data. The business logic of the application, which says what actions to carry out
under what conditions, is embedded in the application server, instead of being
distributed across multiple clients. Three-tier applications are more appropriate
for large applications, and for applications that run on the WorldWideWeb

 



Frequently Asked Questions

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Ans: A transaction is a collection of operations that performs a single logical function in a database application. view more..
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Ans: A database system is partitioned into modules that deal with each of the responsibilities of the overall system. The functional components of a database system can be broadly divided into the storage manager and the query processor components. view more..
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Ans: A relational database is based on the relational model and uses a collection of tables to represent both data and the relationships among those data. view more..
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Ans: The architecture of a database system is greatly influenced by the underlying computer system on which the database system runs. Database systems can be centralized, or client-server, where one server machine executes work on behalf of multiple client machines. view more..
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Ans: The term data mining refers loosely to the process of semi-automatically analysing large databases to find useful patterns. view more..
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Ans: Researchers have developed several data-models to deal with these application domains, including object-based data models and semi-structured data models. view more..
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Ans: A primary goal of a database system is to retrieve information from and store new information into the database. People who work with a database can be categorized as database users or database administrators. view more..
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Ans: Information processing drives the growth of computers, as it has from the earliest days of commercial computers. In fact, automation of data processing tasks predates computers. view more..
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Ans: A relational database consists of a collection of tables, each of which is assigned a unique name. view more..
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Ans: The database schema is the logical design of the database. view more..
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Ans: A super-key is a set of one or more attributes that, taken collectively, allow us to identify uniquely a tuple in the relation. view more..
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Ans: DBMS typically includes a database security and authorization subsystem that is responsible for ensuring the security of portions of a database against unauthorized access view more..
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Ans: The typical method of enforcing discretionary access control in a database system is based on the granting and revoking of privileges. Let us consider privileges in the context of a relational DBMS. view more..
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Ans: This chapter discusses techniques for securing databases against a variety of threats. It also presents schemes of providing access privileges to authorized users. view more..
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Ans: This chapter discusses techniques for securing databases against a variety of threats. It also presents schemes of providing access privileges to authorized users. view more..
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Ans: Object databases is the power they give the designer to specify both the structure of complex objects and the operations that can be applied to these objects view more..
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Ans: XML (Extensible Markup Language)—has emerged as the standard for structuring and exchanging data over the Web. XML can be used to provide information about the structure and meaning of the data in the Web pages rather than just specifying how the Web pages are formatted for display on the screen view more..
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Ans: A database schema, along with primary key and foreign key dependencies, can be depicted by schema diagrams. view more..




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