Infrastructure Development for e-system

Chapter 5

1. What is stored procedures in a database server and why would you create one?         

Ince (2004 p. 107) has suggested that stored procedures are snippets of code which are equivalent to subroutine and they can be written in a variety of languages including SQL, c, C++ and Java. Stored procedures can overcome efficiency problem because they are stored in server and can execute by calling them and  can trigger very quickly over communication medium.

We create stored procedures to make task easy while save time because   it is more efficient in terms of processing time,  it reduce network traffic and it makes updating database easier.

Reference :

Ince, D.(2004). Developing distributed and e-commerce application (2nd ed.). Harlow, W ssex, UK: Addison-Wesley.

2.   What is relational databases ?

In very briefly Ince (2004) describes relational database is a collection of tables and SQL provides facility to access them. A relational database stores data in tables. Tables are organized into colums, and each column store one type of data and the data for a single instance of table is stored as a row. For a eample Student table would have column such as StudentNumber, StudentName, Surname. One record or in other words one row within that table would be something like {1138811, “Dilini”, “Nirosha”}.

(“Relational Databse”, n.d)  has suggested that a relational database stores data in separate tables instead of placing all data in one large table.  A relational database then allows Data Base Administrator’s (DBA’s) to define relationships between these tables.These relationships enable DBA’s to combine data from several tables for querying and reporting.

 Ambler (n.d) has suggested that the easiest way to manipulate a relational database is to submit Structured Query Language statement to it. RDBMS is DBMS which manages a relational database. RDBMS has many advanced features such as object storage, implementing behaviour within the database, Concurrency control, Transaction control, Enforcing referential integrity.

 

Following link for More information.

http://www.agiledata.org/essays/relationalDatabases.html

http://www.tech-faq.com/relational-database.shtml

http://www.wisegeek.com/what-is-a-relational-database.htm

Reference :

Ince, D.(2004). Developing distributed and e-commerce application (2nd ed.). Harlow, W ssex, UK: Addison-Wesley.

Ambler, S. W. (n.d), Relational Database 101: Looking at the whole picture. Retrieved on June 7^th 2009 from http://www.agiledata.org/essays/relationalDatabases.html

What is Relational Database. n.d  Retrieved on June 7, 2009 from http://www.tech-faq.com/relational-database.shtml

3.     What is distributed database and what are three ways of distributing data and problems with it ?

Ince (2004 p. 110) mentioned that a distributed database is table of database distributed among number network computers. There are two reasons for data distribution.

Serchoracle (2205) has suggested a distributed database is a database in which portions of the database are stored on multiple computers within a network. Users have access to the portion of the database at their location so that they can access the data relevant to their tasks without interfering with the work of others. A centralized distributed database management system (DDBMS) manages the database as if it were all stored on the same computer. The DDBMS synchronizes all the data periodically and, in cases where multiple users must access the same data, ensures that updates and deletes performed on the data at one location will be automatically reflected in the data stored elsewhere.

Databases are distributed because

1. To enhance performance
2. Able to create separate database using isolated tables.

Three ways of data distributing are downloading, replication and fragmentation. Downloading is coping data from central repository to another location. Replication is copies of database or part of database place in a specific point in a network. Fragmentation is table of database splits across number of computers.

There are few problems in any distributed environment. Those problems are as follows

• Main problem that have to be solve is security as there are large number of computers.
• Keeping all replicated data up to date without compromising performance.
• Ensuring concurrent access to a database without any incorrect data.
• Some times timing problems occurs because clocks in the computers connected to the system may be out of synchronisation with each other.
• Reliability is also problem because any simple change of one particular transaction could be affect to number of databases

References:

Ince, D.(2004). Developing distributed and e-commerce application (2nd ed.). Harlow, W ssex, UK: Addison-Wesley.

 Serchoracle (2005). Distributed Database.  Retrieved on June 7, 2009 from http://searchoracle.techtarget.com/sDefinition/0,,sid41_gci933754,00.html