Relational Database Management System

A relational database (RDB) is a way of structuring information in tables, rows, and columns. An RDB has the ability to establish links—or relationships–between information by joining tables, which makes it easy to understand and gain insights about the relationship between various data points.^[2]

At heart, a typical RDBMS has five main components:^[1:1]

• Client Communications Manager: to establish and remember the connection state for the caller (be it a client or a middleware server), to respond to SQL commands from the caller, and to return both data and control messages (result codes, errors, etc.) as appropriate.
• Process Manager: whether the system should begin processing the query immediately, or defer execution until a time when enough system resources are available to devote to this query.
• Relational Query Processor: This set of modules checks that the user is authorized to run the query, and compiles the user’s SQL query text into an internal query plan. Once compiled, the resulting query plan is handled via the plan executor. The plan executor consists of a suite of “operators” (relational algorithm implementations) for executing any query.
• Transactional Storage Manager: manages all data access (read) and manipulation (create, update, delete) calls. The storage system includes algorithms and data structures for organizing and accessing data on disk (“access methods”), including basic structures like tables and indexes. It also includes a buffer management module that decides when and what data to transfer between disk and memory buffers.
• Shared Components and Utilities