Oracle Database

Client failure (PMDS)

-Records are locked by any client performing insertions, deletions, or updates. -Locked records are not available to the other clients. -The locked records stay locked in the event of a client failure. -The transactions in progress at the time of failure are loss. - All users have to log off during the repair. -Data can be restored from the last backup, but the transactions since the last backup are lost and have to be reentered

Server Failure (Client/Server)

A central transaction log keeps a log of all current database changes

Client (PMDS)

Adds, deletes, and updates data

Server (Client/Server Databases)

Adds, deletes, updates, and filters data

Structured Query Language

Fourth generation, high-level, nonprocedural language

Client/Server Databases

Multiuser environment - runs the DBMS as a process on the server and runs a client database application on each client

Client Failure (Client/Server)

Only the fail client's transactions in progress are lost

Network Environment (Client/Server)

The client does not store any database. The server sends only requested data to client and less network traffic.

total dependency

a nonkey column is dependent on all primary key columns

transitive dependency

a nonkey column is dependent on another nonkey column

partial dependency

a nonkey column is dependent on part of the primary key

normalization

analyze tables

Optimistic table locking (PMDS)

assumes that no two transactions will happen at the same time on one table

associative entity

decomposition involves a third party; also known as a composite entity

EF Codd

developed relational databases

Higher normal form

lower redundancy

Decomposition

many-to-many relationships are allowed, but they are not easy to implement

third normal form

no transitive dependency

Database Management System (DBMS)

performs the required processing

Relational algebra

procedural language; uses a set of operations on tables to produce new resulting tables

Personal Database Management Systems (PDMS)

stored on a user's desktop computer or client computer

Network environment (PMDS)

system response depends on the speed of the network and amount of traffic

first normal form

table contains no multivalued columns

second normal form

there is no partial dependency. A nonkey column that is dependent on part of a composite key. Exists only in a table with a composite key

Purpose of Relational Database

to overcome the problem of 3rd generation high level language. Only 1 row of a table could be manipulated; Benefit: eliminated the need for a looping structure

Automatic table locking

two agents may not sell the same seat at the same time