In today’s videos, I learned a lot of things, and here I want to talk about the characteristics of the Database management system. It is an efficient, reliable, convenient and safe multi-user storage, it provides access to massive amounts of persistent data. For the characteristics, the first is it is highly prevalent, because of the improvement of the computer science, and the number of data is increasing very fast, right now, terabytes of data are processed almost every day. And because this number of data is larger than normal computers’ memory, the database was designed to handle data residing outside of memory. The second, it is persistent, it means the data in the database outlives the programs that execute on that data. For example, when we run a program, the program end, the data vanished, but, when we run a program based on the database, the program end, the data are still there. The third, safety, should have some mechanisms which can ensure the data remain consistent when some failures happened. For example, when the bank’s electronic outages, they should keep the number of monies stored in the users’ accounts stay consistent. Then, the fourth characteristic, multi-user, the database should allow many applications run based on one database at the same time, and for a single application, it should be allowed to use by different users, then there should be some mechanisms to ensure the data that stored in the database stay consistent. The fifth characteristic, convenience, the database should to simplify the process of a large number of data, it should be easy for the user to use, which means users do not have to type in the algorism to access the data he wants to get. The sixth, Efficiency, because the database will process so much data every day, the data will be inquired and refreshed every second, and this kind of queries and refreshes are simple, stay efficient are very important for a database. The last one, reliable, the database should stay running almost every second for a day. For example, banks and telecommunications, the database of these two are used almost every time in a whole day, to ensure 99.99999% of the time the database is running is very important.