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Chapter 3 - Objectives
Software components of a DBMS. Client–server architecture and advantages of this
type of architecture for a DBMS. Function and uses of Transaction Processing
Monitors. Web-Services and Service-Oriented Architectures Distributed DBMSs
Pearson Education © 2009
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Components of a DBMS
DBMS is partitioned into several software
components/modules– Assigned with to specific operation
– Design of a DBMS must take into account the interface between
the DBMS and the OS
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Components of a DBMSo Query processor
o a major DBMS component that transform queries into a series of low-level instructions directed to the db manager.
o Database Manager (DM)o accepts queries & examines the external
& conceptual schemas to determine what conceptual records are required to satisfy the request
o DM places a call to the file manager to perform the request.
o File managero manipulates the underlying storage files
& manages the allocation of storage space on disk.
o It establishes and maintains the list used, calls on the hashing functions to generate record addresses.
o It passes the requests on to the appropriate access methods(either read or write data from system buffer)
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Components of a DBMSo DML preprocessor
o converts DML statements embedded in an application program into standard function calls in the host language
o DML processor must interact with the query processor to generate the appropriate code
o DDL compiler o converts DDL statements into a set of
tables containing metadata. o These tables are then stored in the system
catalogo Catalog manager
o manages access to and maintains the system catalog
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Components of Database Manager (DM)
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Authorization control –this module checks & confirms whether the user has the necessary authorization to carry out the required operation
Command processor –once the system confirmed the user has authority to carry out operation, control is passed to the command processor.
Integrity checker –for an operation that changes the db, the integrity checker checks whether the requested operation satisfies all necessary integrity constraints.
Query optimizer –determines an optimal strategy for the query execution
Transaction manager –performs the required processing of operations that it receives from transactions
Scheduler –responsible for ensuring that concurrent operations on the db proceed without conflicting with one anotherRecovery manager –ensures that the db remains in a consistent state in the presence of failureBuffer manager –responsible for the transfer of data between main memory & secondary storage (such as disk and tape)
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Multi-User DBMS Architectures
Common architectures used to implement multi-user database management systems:– Teleprocessing
– File-server
– Client-server
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Teleprocessing
Traditional architecture. Single mainframe with a number of terminals attached. User terminals – dumb
– Incapable of functioning on their own
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File-Server
File-server is connected to several workstations across a network.
Database resides on file-server.
DBMS and applications run on each workstation.
Disadvantages include:– Significant network traffic.– Copy of DBMS on each workstation.– Concurrency, recovery and integrity control more
complex.
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File-Server Architecture
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•The processing is distributed about the network (LAN)
•The file-server holds the files required by the applications and the DBMS
•Applications and the DBMS run on each workstation
•File-server acts as a shared hard disk drive
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Traditional Two-Tier Client-Server
Client (tier 1) manages user interface and runs applications. (responsible for the presentation of data to the user)
Server (tier 2) holds database and DBMS. (responsible for supplying data services to the client)
Advantages include:– wider access to existing databases;– increased performance;– possible reduction in hardware costs;– reduction in communication costs;– increased consistency.
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Traditional Two-Tier Client-Server
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•The client takes the user’s request, checks the syntax, and generates database requests in SQL
•Then transmits the message to the server, waits for a response, and formats the response for the end-user.
•The server accepts and processes the database requests, then transmits the results back to the client.
•The processing involves checking authorization, ensuring integrity, maintaining the system catalog, query and update processing.
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Three-Tier Client-Server
In two tier client-server, client side presented two problems preventing true scalability:– ‘Fat’ client, requiring considerable resources on
client’s computer to run effectively.– Significant client-side administration overhead.
By 1995, three layers proposed, each potentially running on a different platform.
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Three-Tier Client-Server
The three layers:– User interface layer– Business logic and data processing layer:
Application Server– DBMS-stores data required by middle tier:
Database Server
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Three-Tier Client-Server
Advantages: – ‘Thin’ client, requiring less expensive hardware.– Application maintenance centralized. – Easier to modify or replace one tier without
affecting others. – Separating business logic from database functions
makes it easier to implement load balancing. – Maps quite naturally to Web environment.
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Transaction Processing Monitors
Program that controls data transfer between clients and servers in order to provide a consistent environment, particularly for Online Transaction Processing (OLTP).
Middleware component that provides access to the services of a number of resource managers (DBMSs, OS, User interfaces, messaging software)
Provide a uniform interface for programmers who are developing transactional software (Software that guarantees that all appropriate databases are updated from a single transaction)
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Transaction Processing Monitors Advantages:
– Transaction routing: increase scalability by directing transactions to specific DBMSs
– Managing distributed transactions: manage transactions that require access to data held in multiple, possibly heterogeneous DBMSs.
– Load balancing: balance client request across multiple DBMSs
– Funneling: handle large users– Increased reliability: act as Transaction Manager,
performing necessary actions to maintain the consistency of the database
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Web Services
A software system designed to support interoperable machine-to-machine interaction over a network
Examples:– Microsoft Virtual Earth Web services– Amazon S3– Geonames– DOTS web services
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Web Services: Microsoft Virtual Earth Web services
Offer static map images match addresses to the map, search for points of
interest, integrate maps and imagery, return driving directions, and incorporate other location intelligence into your Web application.
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Web Services: Amazon S3
Simple web services interface Can be used to store and retrieve large amounts of
data from anywhere on the web Give developer access to the same highly scalable,
reliable, fast, inexpensive data storage infrastructure
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Web Services
Use these technologies and standards:– XML – SOAP (Simple Object Access Protocol) – communication
protocol for exchanging structured information over the Internet and uses a messages format based on XML
– WSDL (Web Services Description Language) protocol – based on XML, used to describe and locate a Web service.
– UDDI (Universal Discovery, Description and Integration) protocol – platform-independent , XML-based registry for businesses to list themselves on the Internet.
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Web Services
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Web Service Web service directory (UDDI)
XML Interface (WSDL)
WSDL documents
Client Application
XML Interface (WSDL)
Internet
2. Publish
1. Generate
3. Find
4. Invoke
SOAP
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Web Services
The growing success of Web services is due to a number of factors, including those below. – Systems can interact with one another dynamically via
standard Internet technologies. – Services are built once and reused many times. – Services can be implemented in any programming
language. – Service consumers do not need to worry about firewalls
because communication is carried over HTTP. – Systems can advertise their capabilities for other systems
to use.
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Distributed Database and DBMS
Distributed Database– A logically related collection of shared data (and description
of this data), physically distributed over a computer network
Distributed DBMS– The software system that permits the management of the
distributed database and makes the distribution transparent to user
Distributed Processing– A centralized database that can be accessed over a computer
networkPearson Education © 2009
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Characteristics of DDBMS
A collection of logically related shared data Data split into a number of fragments Fragments may be replicated Fragments/replicas are allocated to sites Sites are linked by a communication network Data at each site is under control of a DBMS DBMS at each site can handle local applications
autonomously Each DBMS participates in at least one global
applicationPearson Education © 2009
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Data Warehousing
A consolidated/integrated view of corporate data drawn from disparate operational data sources and a range of end-user access tools capable of supporting simple to highly complex queries to support decision making
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Data Warehousing Architecture
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Warehouse Manager
Warehouse Manager
Load Manager
QueryManager
Operational Data Source 1
Archive/Backup Data
Operational Data Source 2
Operational Data Source 3
Operational Data Source 4
Metadata
Detailed Data
Lightly Summarized Data
Highly Summarized
Data
Reporting, query, application development
and EIS tools
OLAP tools
Data Mining tools
End-user Access Tools