Database System Overview and DBMS

Database System Overview

• A database is a collection of related data.
• A large database can be maintained by commercial organizations like Amazon.com.
• Amazon's database has over 20 million books, CDs, videos, DVDs, games, electronics, apparel, and other items.
• The database occupies over 2 terabytes of storage and is stored on 200 servers.
• Around 15 million visitors access Amazon.com daily and use the database to make purchases.
• About 100 people are responsible for keeping the Amazon database up-to-date.

Database Management System (DBMS)

• A DBMS is a software package or system that facilitates the creation and maintenance of a computerized database.
• A database system consists of the DBMS software, the database itself, and sometimes the applications that use them.

Real-Time Databases

• A Real-Time Database processes workloads whose state is constantly changing, such as stock markets.

Mini-World

• A mini-world represents a real-world aspect, such as student grades and transcripts at a university.
• A database should accurately and reliably reflect the mini-world it represents, updating changes as soon as possible.

Transaction

• A transaction is an executing program or process that includes one or more database accesses, such as reading or updating records.

Examples of Databases

• A simple database might have just a few hundred records, like names and addresses.
• A large library catalog may contain half a million entries, organized by primary author, subject, and title.
• The Internal Revenue Service keeps a database of tax forms for 100 million taxpayers, encompassing a large volume of information.

Main Characteristics of a Database

• Database systems should support multiple views of the data.
• Data should be shared and accessed by multiple users simultaneously through multi-user transaction processing.
• The DBMS should ensure that transactions are executed correctly or aborted.
• The DBMS should ensure that changes made by transactions are permanently recorded in the database.
• Online Transaction Processing (OLTP) is crucial for database applications, allowing hundreds of concurrent transactions per second.
• Each transaction should be isolated from other transactions, as if executed individually, even when executing concurrently.
• Every transaction must be executed fully or not at all, ensuring atomicity.

Database Users

• Database users are categorized into actors on the scene and workers behind the scenes.

Actors on the Scene

• Database administrators authorize access, manage resources, and monitor system efficiency.
• Database designers define the content, structure, constraints, and functions of the database, collaborating with end-users to understand their needs.
• End-users interact with the data, querying, reporting, and updating the database content.

End-user categories

• Casual users: access the database occasionally as needed.
• Naïve or parametric users: use pre-defined functions, such as bank tellers or reservation clerks who perform canned transactions.
• Sophisticated users: are familiar with the system and utilize tools to access and manipulate data.
• Stand-alone users: maintain personal databases using packaged applications.

Benefits of using a Database Approach

• Enforces standards for naming, display formats, and meta-data across all data.
• Reduces application development time by leveraging existing structures and functions.
• Allows flexibility to change data structures according to new requirements.
• Ensures the availability of current information for online transaction systems.

When not to use a DBMS

• High initial investment cost.
• Overhead associated with providing security, concurrency control, recovery, and integrity functions.
• Simple, well-defined applications that are not expected to change.
• Embedded systems with limited storage capacity.
• When multiple user access is not required.

Conclusion

Database systems have become essential tools for managing and processing large datasets, enabling efficient storage, retrieval, and manipulation of data in a variety of applications. The database approach promotes standardization, efficiency, and flexibility, making it a fundamental technology for many organizations. There are still situations where a DBMS may not be necessary, but its benefits make it a valuable choice for most data management tasks.

Explore the fundamental concepts of database systems and database management systems (DBMS). Understand how large databases like Amazon's are maintained and accessed by millions of users daily. Learn about real-time databases and their applications in dynamic environments.