4.10 Fundamentals of DB (Client Server Databases) Flashcards
What is a client-server database
A multi-user database, which allows various users can access it from different locations at the same time.
How is a client-server databases managed
- They are managed by a DBMS (Database Management System)
What is the lost update problem
Where concurrent access of a record in a database causes the update of one transaction to be overwritten by the other
What is concurrent access
When multiple users make transactions on the same record at the same time
What is a DBMS
Software that enables the management of all aspects of a database
What is the main problem with client server databases
- Concurrent access can result in the problem of
updates being lost if two clients edit a record at
the same time
What are the different ways concurrent access can be managed
- Record Locks
- Serialisation
- Commitment Ordering
- Timestamps
What is a non-distributed system
where all the parts of the system are in the same physical location
What are the three methods used in a non-distributed client server database to prevent the lost update problem
- Serialisation
- Record Locks
- Timestamps
What is the method used in a distributed client server database to prevent the lost update problem
- Commitment Ordering
Why is commitment ordering used for distributed client server databases
- Commitment ordering is more effective when there are a higher volume of people using the database concurrently
What is a transaction
A unit or request made by a user on a database
