DAT 390 Wk 1 – Practice: Reading

Accurately complete the 1.1 to 1.7 Reading, Participation, and Challenge Activities to receive full points for this practice. You have unlimited attempts. The points you see in zyBooks do not reflect the points you receive in the gradebook.

Storage media

Computers use a variety of media to store data, such as random-access memory, magnetic disk, optical disk, and magnetic tape. Computer media vary on four important dimensions:

• Speed. Speed is measured as access time and transfer rate. Access time is the time required to access the first byte in a read or write operation. Transfer rate is the speed at which data is read or written, following initial access.
• Cost. Cost typically ranges from pennies to dollars per gigabyte of memory, depending on the media type.
• Capacity. In principle, any media type can store any amount of data. In practice, capacity is limited by cost. Expensive media have limited capacity compared to inexpensive media.
• Volatility. Volatile memory is memory that is lost when disconnected from power. Non-volatile memory is retained without power.

Three types of media are most important for database management:

• Main memory, also called random-access memory (RAM), is the primary memory used when computer programs execute. Main memory is fast, expensive, and has limited capacity.
• Flash memory, also called solid-state drive (SSD), is less expensive and higher capacity than main memory. Writes to flash memory are much slower than reads, and both are much slower than main memory writes and reads.
• Magnetic disk, also called hard-disk drive (HDD), is used to store large amounts of data. Magnetic disk is slower, less expensive, and higher capacity than flash memory.

Main memory is volatile. Flash memory and magnetic disk are non-volatile and therefore considered storage media. Databases store data permanently on storage media and transfer data to and from main memory during program execution.