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Flashcards by kai.kullwitz, updated more than 1 year ago
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Created by kai.kullwitz
almost 9 years ago
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| Question | Answer |
| Hard Disk Drive (Magnetic Disk) | - data storage device used for storing and retrieving digital information - consists of one or more rigid ("hard") rapidly rotating disks with magnetic heads arranged on a moving actuator arm to read and write data to the surfaces |
| Hard Disk Structure | - Block, cylinder and sector structure - Block contains 512 bytes |
| Seek Time | Average Time to change from a random track to another track (3-12 msec) |
| Latency Time | Time to mechanical change track, depends on rotation speed, half period of rotation (5-2 msec) |
| RAID (Redundant array of independent disks) | - storage technology that combines multiple disks drive components into logical unit for the purpose of data redundancy and performance improvements - Data distributed across the drives in one or several ways, referred to as RAID levels |
| RAID 0 (block level striping) | - no redundancies - improved performance and additional storage - no fault tolerance - any drive failure destroys whole array |
| RAID 1 (mirroring without parity or striping) | - data written identically to two drives, producing a "mirrored set" - read request is serviced by either of the drives |
| RAID 5 (block level striping with distributed parity) | - distributes parity along with the data - not destroyed by single drive failure - any subsequent reads can be calculated from the distributed parity, in case of failure - at least 3 disks |
| Flash Memory | - also Computer memory - particular type of "electronically erasable programmable read-online memory" (EEPROM) - often used in portable electronics |
| Flash Memory - Speed Advantage | - differs from regular EEPROM because it can delete data in entire blocks - preferable technology for applications that require constant, large data updates |
| Flash Memory - General Advantages | - non volatile, solid state - no moving parts - silent - smaller than HDD - highly portable - much faster access time |
| File System | - used to control how information is stored and retrieved - without it -> one large body of information where we don't know the end and the beginning - part of operating system |
| Operating System | - collection of software - manages computer hardware resources - provides common service for computer programs |
| Cloud Computing (CC) | - synonym for distributed computing over a network - ability to run programs on many computers at the same time |
| Cloud Clients | Applications work like with every other operating system Customized operation system is accessible from everywhere in the internet |
| Software as a Service (SaaS) | users are provided access to application software and databases (CRM, Email, communication, games, virtual desktop) |
| Platform as a Service (PaaS) | - Cloud providers deliver a computing platform - typically including operation system, database and web server |
| Infrastructure as a Serice (IaaS) | - providers of IaaS offer computer-, physical or virtual machines and other resources |
| Properties of CC | - On demand Self-Service - Broad Network Access - Ressource Pooling - Rapid elasticity - Measured service |
| Database Application Examples - Traditional Database Application | Store textual or numeric information |
| Database Application Examples - Multimedia Databases | Store Images, audio clips Video streaming digitally |
| Database Application Examples - Geographical information systems (GIS) | Store and analyse maps, weather data and satellite images |
| Database Application Examples - Data Warehouses and analytical processing (OLAP) systems | Extract and analyse useful business information from very large databases Support decision making |
| Database Application Examples - Real-Time and active database technology | Control industrial and manufacturing processes |
| Database Application Examples - Large Commercial Database | Amazon.com |
| Database (DB) | organized collection of Data |
| Database management systems | specially designed applications interacting with the user, other applications and the database itself to capture and analyse data software designed to allow the definitions, creation, querying and update and administration of databases well know DBMS: MySQL, SQLite, Oracle, SAP standards like "SQL" allow applications to work with more than one DB enables users to create and maintain a DB |
| Query | Causes some data to be retrieved |
| Transaction | May cause some data to be read and some data to be written into the database |
| Protection | System protection Security protection |
| Maintain a database system | Allow the system to evolve as requirements change over time |
| Simplified Database System environment | |
| Phases for designing a database | 1. Requirements specification and analysis 2. Conceptual design 3. Logical Design 4. Physical desingn |
| Traditional File processsing | Each user defines and implements the files needed for a specific software application |
| Database Approach | Single repository maintains data that is defined once and then accessed by various users |
| Main characteristics of Database Approach | self describing nature of database system Insulation between programs, data and data abstraction Support of multiple views of the data Sharing of data and multiuser transaction processing |
| Defining a database | Specify the data types, structures and constraints of the data to be stored |
| Meta-data | Describes structure of the database |
| Manipulating a database | Query and update the database |
| Application program | Accesses database by sending queries to DBMS |
| Database catalog used by ... : | DBMS Software Database users who need information |
| Program-data independence | Structure of data files is stored in DBMS catalog separately from access programs |
| Program-operation independence | - Operation specified in two parts * Interface includes operation name and data types of its arguments * Implementation can be changed without affecting the interface |
| Data Abstraction | Allows program-data independent and program-operation independence |
| Sharing of data and multiuser Transaction Processing | Allow multiple users to access the database at the same time |
| Concurrency Control Software | Ensure that several users trying to update the same data do so in a controlled manner Result of the updates is correct |
| Isolation property | Each transaction appears to execute in isolation from other transactions |
| Atomicity property | Either all the database operations in a transaction are executed or none are |
| Database administrators (DBA) are responsible for: | Authorizing access to the database Coordinating and monitoring its use Acquiring software and hardware resources |
| Database designers are responsible for: | Identifying the date to be stored Chosing appropriate structures to represent and store this data |
| End users | People whose jobs will require access to the database ( Casual end users) (Naive or parametric end users) (Sophisticated end users) (Standalone users) |
| System analysts | Determine requirements of end users |
| Application programmers | Implement these specification as programs |
| DBMS system designers and implementers | Design and implement the DBMS modules and interfaces as a software package |
| Tool developers | Design and implement tools |
| Operation and maintenance personnel | Responsible for running and maintenance of hardware and software environment for database system |
| Controlling Redundancy | Data Normalization De-normalization |
| Backup and recovery subsystem | responsible for recovery |
| Enforcing integrity contraints - Referential integrity constraint | Every section must be related to a course record |
| Enforcing integrity contraints - Key or uniqueness constraint | Every course record must have a unique value for Course_number |
| Data abstraction | Suppression of details of data organization and storage Highlighting of the essential features for an improved understanding of data |
| Data Model | Collection of concepts that describe the structure of a databases Provides means to achieve data abstraction |
| High level / conceptual data models | Close to the way many users perceive data |
| Low Level or physical data models | Describe the details of how data is stored on computer storage media |
| Representational data models | Specify retrievals and updates on the databse |
| Entity | Represents a real-world object or concept |
| Attribute | Represents some property of interest Further describes an entity |
| Relationship among two or more entities | Represents an association among the entities "Entity-Relationship model" |
| Relational data model | Used most frequently in traditional commercial DBMSs Represents data as a collection of relations |
| Physical Data Model | Describe how data is stored as files in the computer |
| Access Path | Structure that makes the search for particular database records efficient |
| Index | Example of an access path Allows direct access to data using an index term or a keyword |
| Database schema | Description of a database |
| Schema diagram | Displays selected aspects of a schema |
| Database Construct | Each object in the schema |
| Database state / Snapshot | Data in database at a particular moment in time |
| Three Schema architecture | Internal level Describes physical storage structure of the datbase ________________________________________________ Conceptional level Describes structure of the whole database for a community of users ________________________________________________ External / View Level Describes part fo the database that a particular user group is interested in |
| DBMS Languages | Data Definition Language (DDL) Storage definition language (SDL) View definition language (VDL) Data manipulation language (DML) High level or nonprocedural DML Low level or procedural DML |
| Computer-aided software engineering (CASE) | application of a set of tools and methods to software system desired result: high quality, defect free and maintainable software products |
| Server-types | File Server Printer Server Web / Email servers |
| Client machines | Provide user with: - Appropriate interfaces to utilize these servers - Local processing power to run local applications |
| Server | System containing both hardware and software Provides services to the client machines (file access, printing, archiving, database access) |
| JDBC | Allows Java client programs to access one more DBMS through Stnadard interface |
| ODBC (Open Database Connectivity) | Provides application programming interface (API) Allows client-side programs to call the DBMS (Client and Server machines |
| Relation Data Model - Row | Represents a collection of related data values Tuple |
| Relation data model - Attribute | Meaning of the values in each row |
| Relation Dartabase Model - Cardinality | Total number of values in domain |
| Relation Database Model - Constraint | Restrictions on the actual values in a database state Derived from the rules in the mini world that the database represents |
| Relation Database Model - Superkey | No two tuples can have the same combination of values for all the attributes No two distinct tuples in any state r of R can have the same value for SK |
| Relation Database Model - Key | Superkey of R Removing any attribute A from K leaves a set of attributes K that is not a superkey of R any more |
| Relation Database Model -Minimal superkey | Cannot remove any attributes and still have uniqueness constraint in above condition hold |
| Relation Database Model - Candidate Key | Relation schema may have more than one key |
| Relation Database Model - Primary key | Desginated among candidate keys Underline attribute |
| Relation Database Model - Entity integrity constraint | No primary key value can be NULL |
| Operations of the relational model | Operations of the relational model can be categorized into retrievals and updates |
| Basic operations that change states of relations | Insert Delete Update |
| INSERT Operation | Provides a list of attribute values for a new tuple t that is to be inserted into a Relation R Can violate any of the four types of constraints If insertion violates one or more constraints the insertion is rejected |
| SQL language | major reasons for the commercial success of relational databases |
| SQL | Structured Query Language Statements for data definitions, queries and updates |
| CREATE statement | Main SQL command for data definition |
| CREATE SCHEMA statement |
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