Exam 1 Cs 460

1.) database

2.)DBA (database administrator)

3.) Application Programs

4.) Hardware ( storage, servers, etc)

1.) data sharing

2.) centralized control

3.) Redundancy control

4.) Data Integrity

5.) Data security

6.) Views

7.) Data independence (logical data, physical data)

The overall description of a database (at various granularities)

A description of DBMS components and their interconnections

describes user perspectives of the DB

design of the field groupings, data relationships, etc.

define record sizes, representatives, indices,etc.

Hidden from application programs, users

(view to view) often easier to tweak an existing view. but efficiency is a concern

allows field renaming, arrangements for user benefits

Convert logical structure to physical representations

Provides physical data independence

Client- presentation of data to user

Server- fields requests from clients, runs the DBMS

-more capabilities

-distribution

-less client computing needed

Service Oriented Architectures

software design technique

Apps are built using pre written service mods

Goal is to be flexible with the adoption of new business processes

Advertising (service)

Finding

Using

Each server has all or some, or none of the DB stored locally

Seek Time

Rotational delay

Transfer Time

1 Write

2 copies

Adv: can operate w/ failed drive (possibly read in parallel)

Disadv: Cost (2 disks, capacity of one)

distributing units of data across disks

Adv. Performance

Disadv. Inc probability of drive failure

p(A ^ B) = p(A) + p(B) - p(A) * p(B)

A file containing structured references to records of another file.

The # of whole records that can be stored in a block. bf - (block size/ record size)

Unallocable storage within an allocation unit.

similar to unpacked but you need ptrs in the directory w/ offsets

A file containing structured references to records of another file

A key able to uniquely identify a record (i.e. Student ID, SSN)

The chosen Candidate key to be the records identifier

Any non-candidate key

The key used to sort the files records

Single (sorted file)

Multi-level (B+ tree)

Candidate Key

a candidate key

a candidate key

not a candidate key (therefore, secondary)

a secondary key

any field

any field

any field

Hold a record for every DB file record

permits existence queries w/ index only

indices have only a subset of the field values

Therefore: smaller, faster to search

If leaf has capacity insert,

otherwise, form new set for keys, promote median value to parent, create two nodes that are less than and greater than. Attach children on either side

second level: 5 * 4 = 20

Third level: 5^2 * 4 = 100

first level: 200

second level: 201 * 200

third level: 201^2 * 200

Copies of some keys occupy internal nodes

each key is stored in a leaf node

leaf nodes are linked sequentially

Adv: built in disk pointers for all key values, Supports exact match (10-20)

DisAdv: Waste of storage capacity

Insertion/ Deletions are a little more complex

A null is a marker that indicates that a field does not have a value.

A field in one file whose values are drawn from the primary key field of another file

Foreign

the DB is defined

null

1: Requirements Analysis

2: Conceptual Design

3: Logical Design

4: Physical Design

An Entity is an instance of a general classification

Ex. Each of you is an instance of class "human"

Ex. Instructors teach classes

In a 1 to 1 relationship between two entity sets A and B, an entity from A is associated with at most one entity from B, and an entity from B is associated with at most one entity from A.

An M to N relationship is a pair of 1 to N relationships

3 degree or 3 way. Ex. SPJ schema

Hierarchical

Network

Relational

Object