The article explains how a Real-Time Database System (RTDB) combines regular database tech with real-time systems to form a Supervisory Information System (SIS). Historical data is info sampled from RTDB and stored in a historical database for users to access. This database includes memory and disk-based parts. The memory bit organizes short-term data, while the disk part handles historical data and management files. In the disk section, they talk about file structures and buffer zones. They also detail the essential functions like data read/write, compression, and how to access data pages.