The Database Management System (DBMS)
| English | Chinese | Pinyin |
|---|---|---|
| DBMS | 数据库管理系统 | shù jù kù guǎn lǐ xì tǒng |
| data dictionary | 数据字典 | shù jù zì diǎn |
| transaction | 事务 | shì wù |
| concurrency control | 并发控制 | bìng fā kòng zhì |
| view | 视图 | shì tú |
The DBMS 数据库管理系统
- A Database Management System (DBMS) is the software that manages the database centrally.
- It is what fixes the flat-file problems — one place controls all the data.
- Many programs and users share it safely.
Database service lab
Watch how a DBMS turns a query into safe shared data access.
What a DBMS provides
- Data dictionary 数据字典 — a description of every table, field, type and key; programs query it instead of hard-coding the structure.
- Redundancy/consistency control — each fact stored once.
- Concurrent access control — locks and transactions 事务 let many users work at once.
- Backup and recovery, security and per-user permissions, and centrally enforced integrity rules (keys, unique/range constraints).
The database approach: one DBMS serves all the programs
A data dictionary in a DBMS holds:
The data dictionary describes the database structure, so programs query it rather than hard-coding the layout.
Match each DBMS service to what it does.
A DBMS bundles these services so programs never touch the raw files directly.
Transactions and concurrency
- A transaction is a group of operations that all succeed or all fail — no half-finished updates.
- Concurrency control 并发控制 uses locks so two users can't corrupt the same record at once.
- A view 视图 is a virtual table that shows each user only "their" slice of the data.
A database transaction is:
Transactions are all-or-nothing, so the database is never left half-updated.
Concurrency control (locking) is needed so that:
Locks stop two simultaneous updates from clashing and corrupting shared data.
A transaction is all-or-nothing: it either fully completes (commit) or fully undoes itself (rollback), so the database is never left half-updated.
This atomicity is why a bank transfer can never debit one account without crediting the other.
A virtual table (often a saved query) that shows a user only their relevant slice of the data is called a ______.
A view presents a tailored, often restricted, slice of the data without copying it.
DBMS tools
- A query builder and SQL editor to ask questions of the data.
- A forms builder for data entry and a report generator for output.
- A data-dictionary editor and user management.
- A DBMS provides data management and data modelling (a logical schema), data integrity and data security, a query processor and a developer interface.
You've got it
- a DBMS manages the database centrally for all programs/users
- the data dictionary describes the structure so programs don't hard-code it
- a transaction is all-or-nothing; concurrency control (locks) protects shared data
- a view gives each user a tailored slice of the data