Database Internals

Chapter 1. Introduction and Overview

Database management systems can serve different purposes: some are used primarily for temporary hot data, some serve as a long-lived cold storage, some allow complex analytical queries, some only allow accessing values by the key, some are optimized to store time-series data, and some store large blobs efficiently. To understand differences and draw distinctions, we start with a short classification and overview, as this helps us to understand the scope of further discussions.

Terminology can sometimes be ambiguous and hard to understand without a complete context. For example, distinctions between column and wide column stores that have little or nothing to do with each other, or how clustered and nonclustered indexes relate to index-organized tables. This chapter aims to disambiguate these terms and find their precise definitions.

We start with an overview of database management system architecture (see “DBMS Architecture”), and discuss system components and their responsibilities. After that, we discuss the distinctions among the database management systems in terms of a storage medium (see “Memory- Versus Disk-Based DBMS”), and layout (see “Column- Versus Row-Oriented DBMS”).

These two groups do not present a full taxonomy of database management systems and there are many other ways they’re classified. For example, some sources group DBMSs into three major categories:

Online transaction processing (OLTP) databases

These handle a large ...