Database System Overview

Database management systems are a critical component of any information management system.

What is a database management system? Simply put, a database management system is a software system that can effectively manage large amounts of data, allowing multiple users to simultaneously and efficiently access and use data.

The Halo database consists of a database instance and a database cluster:

• Database instance: A collection of memory structures and background processes.

• Database cluster: A collection of database files. It can exist independently of the database instance.

Figure 1-1 Halo Database Architecture

Figure 1-1 illustrates the architecture of the Halo database. The database instance primarily consists of a shared memory area, a local memory area, and a series of background processes. The shared memory area is mainly composed of shared buffers and transaction log buffers. The background processes mainly include the Background Writer (data write process), WAL Writer (transaction log write process), Checkpointer (checkpoint process), Statistic Collector (statistics collection process), Autovacuum (automatic cleanup process), and Backend Process (session process), among others. The database cluster is primarily composed of data files, transaction log files, and various auxiliary files.