Chapter Objectives
In this chapter, you will learn to:
• identify the key components of a DBMS architecture;
• understand how these components work together for data storage, processing, and management;
• categorize DBMSs based upon data model, degree of simultaneous access, architecture, and usage.
Opening Scenario
To kick-start its business, Sober purchased the customer database of Mellow Cab, a firm that recently stepped out of the taxi business. Unfortunately, the database has been handed over in a legacy CODASYL format that Sober is not familiar with. Sober also needs a new database to store transaction details whenever passengers book either a ride-hailing or ride-sharing service. Other data (e.g., multimedia) are an option they are interested in. Sober wants to continuously store the location of its taxis and periodically review hot-spot pick-up and drop-off locations. Sober is looking at ways to manage all these data sources in the optimal way.
As discussed in Chapter 1, a DBMS supports the creation, usage, and maintenance of a database. It consists of several modules, each with their specific functionality, that work together according to a predefined architecture. In this chapter, we zoom into this internal architecture and provide a categorization of DBMSs along various dimensions. The overview of the chapter is straightforward. We start by discussing the components that together make up a DBMS. Next, we provide a classification of DBMSs in terms of data model, degree of simultaneous access, architecture, and usage.
Architecture of a DBMS
As discussed before, a DBMS needs to support various types of data management-related activities, such as querying and storage. It also must provide interfaces to its environment. To achieve both of these goals, a DBMS is composed of various interacting modules that together make up the database management system architecture. Figure 2.1 shows an overview of the key components of a DBMS architecture. We review each component in more detail in what follows.
Figure 2.1 is by no means exhaustive. Depending upon the vendor and implementation, some components may be left out and others added. On the left, you can see various ways of interacting with the DBMS. DDL statements create data definitions that are stored in the catalog. Interactivequeries are typically executed from a front-end tool, such as a command-line interface, simple graphical user interface, or forms-based interface. Applications interact with the DBMS using embedded DML statements.
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