Introduction Flashcards
What is a database?
Collection of data that conforms with a data model (eg relational data model)
What is a database management system?
Software designed to store, manage, and facilitate access to databases.
What are the differences between a file system and DBMS?
- Disk Space and Buffer Management
- Efficient Data Access
- Concurrent Access and Crash Recovery
- Application/Query Development Time
What is a data model?
A collection of concepts for describing data.
What is a schema?
A description of a particular collection of data, using a given data model.
What are the 3 levels of abstraction for databases?
- External schema (views) that describe how users see the data.
- Conceptual (Logical) scheme that defines logical structure (Relation scheme)
- Physical Schema describes the files and indexses used. (unordered files etc)
What is logical data independence?
Protection from changes in the logical structure of data (between views and conceptual schema)
What is physical data independence?
Protection from changes in physical structure of data (between conceptual and physical schema).
Which changes faster: the DB application or the platform?
The rate of change of DB applications is incredibly slow and thus the platorm changes faster.
Wthat are 3 types of file organizations used in DBMS?
Heap files, sorted files, clustered files
What are 3 typesof indexes used in DBMS?
B-tree, Hash, and Inverted
What is ACID?
Atomicity (write after lock)
Consistent (IC)
isolation (locking protocol)
Durability (write after lock)
What are the 5 layers of an RDBMS?
- Query Optimization and Execution
- Relational Operators
- File and Access Methods
- Buffer Management
- Disk Space Management
Which layers must consider concurrency control and recovery?
File and Access Methods
Buffer Mangement
Disk Space Management
Why not always use DBMS?
1- Expensive/complicated to set up and maintain
- General-purpose; not suited for all tasks
