Ddbms Unit 4

MCA 325, Distributed DBMS And Object Oriented Databases

Bharati Vidyapeeths Institute of Computer Applications and Management, New Delhi-63, by Shivendra Goel U4.1

Distributed Database Management System

Bharati Vidyapeeths Institute of Computer Applications and Management, New Delhi-63,By Shivendra Goel. U4.1

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UNIT-4

Learning ObjectiveHeterogeneous database-federated database, reference architecture, loosely and tightly coupled, Alternative architectures, Development tasks, operation global task management.


operation global task management.Client server databases SQL server, Open database connectivity, Constructing an Application.

Definition: Composed of heterogeneoushardware, operating system databasemanagement system and applications.

Provides logically integrated view of existingheterogeneous distributed databases

Heterogeneous Distributed Database


heterogeneous distributed databases. The three-level architecture of a

Heterogeneous Distributed Database System(HDDMS)



ExternalSchema 1

ExternalSchema 2

ExternalSchema 3

User User User User

Heterogeneous Distributed Database


ConceptualSchema

InternalSchema

Data management system (differentvendors)

Data Models (i.e. relational, text indexing,object)

Query the transaction processing algorithms

Challenges posed by integrating distributed databases


Data types (i.e., text graphics, multimedia,hypermedia)

Format (i.e. Structured, unstructured) Semantics

In a heterogeneous database (HDD), thelocal database is not managed by the samedistributed database management system.Federated Database:A bi ti f t

Challenges posed by integrating distributed databases Cont...


A combination of autonomous,heterogeneous databases that areoperating together



Definition Why do we need database federation Problem with federated database How does database federation work

Federated Databases


Reference Architecture

A collection of databases that are treated asone entity and viewed through a single userinterface.

A federated database system integrates

Definition


y gheterogeneous, autonomous databasesystems, whereby both local applications andglobal applications accessing multiplecomponent database systems are supported.

Such a federated database system is acomplex system of systems which requires awell designed organization at the softwarearchitecture level.

Federated Databases




Significant productivity gains are to be had if youcan work on all the different databases, includingselects, inserts, updates, and deletes as if all thetables lived in a single database. Databasefederation makes the tables look like they are allin the same database.If th l f i i t l d if th

Data Federation


If the volume of queries is not large, and if theycan often can be satisfied with summary tables,there is a huge productivity boost by eliminatingthe need for a data mart and the correspondingneed to create a new server, move significantquantities of data, and so on

Organization of schemas in a schemaarchitecture Organize the managementand stewardship of the various data sets insome way that ensures theirinteroperability

Problems


interoperability.

The "federator" system operates on thetables in the remote systems, the"federatees".

The remote tables appear as virtual tablesin the "Federator" database.

Client application programs can perform

Federated Databases


Client application programs can performoperations on the virtual tables in the"Federator" database, but the realpersistent storage is in the remotedatabase.



Each "federatee" views the "federator" as justanother database client connection. The"Federatee" is simply servicing clientrequests for database operations.

The "federator" needs client software to

Federated Databases Cont


The federator needs client software toaccess each remote database

FEDERATOR FEDERATEE 1 FEDERATEE 2

Members of federation


Figure 1

We wish to consider how contracts written inour framework can interact with oneanother.

Before doing so, let us return to a more

Contract Interactions


intuitive level to see how contracts,unconstrained by our framework, mightinteract. Two contracts are in conflict whenone requires a certain action and the otherprohibits it.



The heart of the federated databaseproblem is to be able to share certain databetween independent organizations withoutgiving up full control of that data.

Typically one organization will permit

The Basic Framework: Granting Rights


Typically, one organization will permitanother organization certain accesses to itsdata provided that the latter organizationagrees to full certain obligations.

A problem that needs addressing is thatobligations imposed by various contractsmay conflict with one another. In thefollowing we present a framework thateliminates potential conflicts between

The Basic Framework: Granting Rights Cont


eliminates potential conflicts betweenobligations by eliminating the need forobligations.

In fact, we simply do not allow forobligations in the framework. One might saythat there is only one global obligation,namely, to abide by the framework. (Wealso make the tacit assumption that an interorganizational access privilege can only be



organizational access privilege can only begranted through a contract.) The desiredeffect will be achieved partly by theparticulars of the contract and partly by thegeneral framework itself. We make noattempt in this framework to address issuesof implementation or assurance.



Specially, we will not be concerned withgeneral mechanisms for guaranteeing thatall parties must abide by the contract,though it will be possible for contracts to bewritten so as to impose some checks and



written so as to impose some checks andbalances toward this end.

For federated database systems, thetraditional three-level database schemaarchitecture must be extended to supportthe dimensions of distributionheterogeneity, and autonomy.

Reference Architecture


g y y It provides the framework in which to

understand, categorize and comparedifferent architectural options for developingspecific systems.

Local Schema: A Local Schema is theconceptual schema of a component databasesystem which is expressed in the (native) datamodel of that component.

Reference Architecture Cont


Component Schema: A Component Schemais a Local Schema transformed into the(canonical) data model of the federation layer.



Export Schema: An Export Schema isderived from a Component Schema anddefines an interface to the local data that ismade available to the federation.



Federated Schema: When Exported Schemasare semantically heterogeneous, it isnecessary to integrate them using anotherlevel. A Federated Schema on this higherlevel is the result of the integration of multipleE t S h th idi i t t d



Export Schemas; thus, providing an integratedview.

External Schema: An External Schema is aspecific view on a Federated Schema or on aLocal Schema. External Schemas may baseon a specific data model different from thecanonical data model. Basically, External



y,Schemas serve as specific interfaces forapplications (local or global).



Loosely & tightly coupled Alternative architecture Development tasks Operation Global task management

Points to be covered


Information systems that provideinteroperation and varying degrees ofintegration among multiple DBs are called.

Multi database systems orFederated systems or

Heterogeneous Distributed Databases


Federated systems orMore generally, heterogeneous distributeddatabase systems (HDDBSs)

User creates and maintains federation schema,Also called Interoperable Database System

Creating schema corresponds to creating a viewagainst relevant export schemasTh f h t b f

Loosely coupled FDBSs


Therefore, each user must be aware ofinformation and structure of the export schemas

Hard to support view updates therefore,assume highly autonomous read-only DBs



Flexibility of different interpretations possiblefor same federated schema

Easier to cope with dynamic changes in

Loosely coupled FDBSs - Advantages


schemas since it is easier to create views.Detection of changes is however expensive.

Duplicated effort in creation of similarfederated schemas.

Difficulty in understanding the semantics ofschemas available to the user.

Loosely coupled FDBSs - Disadvantages


Due to possible multiple view creations,view updating cannot be supported.

Aim: provide location, replication anddistribution transparency

Federation administrators have full controlover creation and maintenance of federatedschemas and access to other export

Tightly coupled FDBSs


schemas and access to other exportschemas

Single federated schema same as globalschema but view updates possible ifadministrators understand the mappings.



FDBS administrator and component DBSsnegotiate creation of export schemasduring which administrator. has completeread access to component schema and/ordata Violates autonomy

Tightly coupled FDBSs Disadvantages


data. Violates autonomy Change in export/component schemas

imply redoing federated schema creation.

System architecture - Core componentscombined in different ways to producedifferent data management architectures Data: Data are the basic facts and

information managed by a DBS. Database: A database is a repository of

More on Federated Databases


Database: A database is a repository ofdata structured according to a data model.

Commands: Commands are requests forspecific actions that are either entered bya user or generated by a processor.

Processors: Processors are softwaremodules that manipulate commands anddata.

Schemas: Schemas are descriptions ofdata managed by one or more DBMSs. A

h i t f h bj t d

More on Federated Databases Cont


schema consists of schema objects andtheir interrelationships.

Mappings: Mappings are functions that correlate the schema objects in one schema to the schema objects in another schema.



Transforming P: Uses mappings totransform commands from internalcommand language to local querylanguage etc.Filtering P: Uses access control specified in

Processors in a FDBS


Filtering P: Uses access control specified inexport schema to limit allowable operationssubmitted to corresponding componentschemas

Constructing P: Performs querydecomposition and merges data

Multiple databases created for the samefunctionality Different operating systems, data formats,

query languages etc

Multi database systems


Typically DBs managed by DBMSs runningon heterogeneous computing platforms

Information sharing across dissimilarplatforms

Interconnect previously isolatedsoftware systems (DBMS)

Multi database systems Cont


software systems (DBMS)Not only invoke but alsocoordinate interactions



Multidatabase has been classified according to the following criteria:

1. Distribution:* Data can be placed in many distributed



databases. * Databases can be found in the same or

different computer systems.

2. Heterogeneity:* This is found in the differences in

technology i.e., software, hardware, and operating system.

* The two types of heterogeneity are those



The two types of heterogeneity are those that are due to:

* differences in various DBMSs* differences in data semantics

3. Autonomy:A component database can have the following

autonomies: Design Autonomy :Choice of data

presentation and attributes.



Communication Autonomy : ability to decide on its own when to communicate with other components of the federated database system.



Execution Autonomy: ability to executesome of its operations locally withoutinfluence by external operations that areexecuted in other component databasesor in the federation database system.



y

Autonomy (A)A0: Tight integrationA1: Semi-autonomousA2: Total isolation

Distribution (D)

Distribution

(A2. D2, H1)

Architectural Alternatives (1)


D0: Non-distributedD1: Client ServerD2: Peer-to-peer

Heterogeneity (H) H0: Homogeneous H1: Heterogeneous

Heterogeneity

Autonomy

(A0. D0, H0)

(A0, D0, H0)A collection of logically integratedDBMSs on the same site, also calledComposite Systems



(A0, D0, H1) Providing integrated access to

heterogeneous systems on a singlemachine



(A0, D1, H0)Client Server distribution

(A0, D2, H0)Fully distributed



(A1, D0, H0) Semi-autonomous systems, also calledFederated Systems. Each DBMS knowshow to participate in the federation

(A1, D0, H1)Heterogeneous Federated DBMSs.

(A1, D1, H1)Distributed Heterogeneous Federated



DBMSs (A2, D0, H0)

Multi-database Systems. Completehomogeneity in component systems isunlikely

(A2, D0, H1)Heterogeneous Multi-databases. Similarto (A1, D0, H1), but with full autonomy



(A2, D1, H1), (A2, D2, H1)Distributed Multi-database Systems



(Ax, D1, Hy)Client Server Architecture

(A0, D2, H0)

Major DBMS Architectures (6)


Peer-to-peer Architecture

(A2, Dx, Hy) Multi-database Architecture

Data management system (differentvendors)

Data Models (i.e. relational, text indexing,object)

Query the transaction processing

Challenges posed by integrating HDDBS


Query the transaction processingalgorithms

Data types (i.e., text graphics, multimedia,hypermedia)

Format (i.e. Structured, unstructured) Heterogeneity in Semantics

Typical Heterogeneous databases include:World Wide WebMultimedia

Preservation of the databases autonomy is

Challenges posed by integrating HDDBS Cont...


paramount. Data access facilities in Heterogeneous



Database Systems can range from:browsing across component databasesquerying a centralised data warehousequerying multiple databases.

A heterogeneous database system can be

Challenges posed by integrating HDDBS Cont...


A heterogeneous database system can beprovided with a multi-database querylanguage.

Semantic Heterogeneity (Different Database designers represent the same object in different ways.) e.g.

Synonyms - same entity different names Homonyms different entities same

Problems in Integrating Heterogeneous Databases


Homonyms - different entities same names

Description Heterogeneity(Different characteristics are used to describethe same object)

M d l H t it

Problems in Integrating Heterogeneous Databases Cont...


Model Heterogeneity(Use of different models to represent thesame data e.g. SSADM, E-R Diagram, UseCases)



Based on complete integration to provide asingle viewAdvantages: Consistent, uniform view of and access to

d t f

Global Schema Integration


data for users Users unaware of existing multiple

existing DBs

Disadvantages Hard to automate creation of a global

schema: structural, semantic orbehavioral conflicts

Autonomy esp association autonomy

Global Schema Integration Cont


Autonomy esp. association autonomysacrificed: all local data and operations tobe revealed

Loss of semantic information depending onhow the schema integration is performed

Correctness of global schema is hard toprove: hard because of context dependentmeanings

Global Schema Integration Cont


meanings



GES : global external schema GCS : global conceptual schema LES : local external schema LCS : local conceptual schema

Acronyms Used


p LIS : local internal schema

Distribute the functionality between client and serverto better manage the complexity of the DBMS

Two-level Architecture

Client Server Architectures


Typical Scenario1.Client parses a query, decomposes into independent site queries, and sends to appropriate server2.Each server processes local query and sends the result relation to client3.Client combines the results of sub-queries Server

Client

User

RequestResponse

A type of network in which each workstationhas equivalent capabilities andresponsibilities.

This differs from client/server architectures,in which some computers are dedicated to

Peer-to-peer Arch.


pserving the others.

Peer-to-peer networks are generally simpler,but they usually do not offer the sameperformance under heavy loads.



Created Late 80s Uniform interface to write client s/w

for relational dbsP l t d t d d f

Open Database Connectivity


Popular - accepted as standard forrelational database

Single API for client application towork with different dbs.

Applications using ODBC API cancommunicate with any relational dbfor which there is an ODBC driver

Compared to other db interfaces it is a lowl l i t f

ODBC API (The Interface)


level interface Enables client application to

configure and control the relational database at a

relatively low level

Limited to relational dbsDue to relational nature, difficult to use for

non-relational data sources, such asObject dbs

ODBC - Limitations


non-relational dbsnetwork directory servicesemail storesetc



ODBC Driver Manager (ODBC32.DLL)Calls functions in the ODBC drivers (DLLs)to perform operations on the database

Import Library (ODBC32.LIB)

ODBC - Provides


Client applications link to it to use functionsexposed by the ODBC driver manager

ODBC header files for the ODBC API

Client

RDBMS Database

Server

ODBC Drivers

ODBC Architecture


Client Application

CodeHost

System

ISAMFiles

ODBCDriver

Manager

ODBC32.DLL

Introduction Transact Sql History Releases Description

SQL Server


Description Future Developments Working



Microsoft SQL Server is a relational databasemanagement system (RDBMS) produced byMicrosoft.

Its primary query language is Transact-SQL,an implementation of the ANSI/ISO standard

Microsoft SQL Server


Structured Query Language (SQL) used byboth Microsoft and Sybase.

SQL Server is commonly used by businessesfor small- to medium-sized databases, but thepast five years have seen greater adoption ofthe product for larger enterprise databases.

Transact-SQL is an extension to the SQLdatabase programming language.

It is a powerful language offering manyfeatures A wide variety of data types

Transact-SQL


A wide variety of data types Temporary objects System and extended stored procedures

Scrollable cursors, Conditional processing, Transaction control, Exception and error handling, and much

Transact-SQL Cont


more



Microsoft, Sybase and Ashton-Tateoriginally teamed up to create and marketthe first version named SQL Server 1.0 forOS/2 (about 1989) which was essentially thesame as Sybase SQL Server 3.0 on Unix,VMS t

History


VMS, etc. Microsoft SQL Server 4.2 was shipped

around 1992 (available bundled withMicrosoft OS/2 version 1.3). Later MicrosoftSQL Server 4.21 for Windows NT wasreleased .

Microsoft SQL Server v6.0 was the firstversion of SQL Server that wasarchitected for NT and did not includeany direction from Sybase.

History Cont


Later, Sybase changed the name of itsproduct to Adaptive Server Enterprise

SQL Server 7.0 was the first true GUI baseddatabase server .

The current version, Microsoft SQL Server2005, was released in November of 2005.

Advancements have been made in

History Cont


Advancements have been made in performance, the client IDE tools, and



several complementary systems that arepackaged with SQL Server 2005. These include: an ETL tool (SQL Server Integration

Services or SSIS), a Reporting Server,

History Cont


an OLAP and data mining server (AnalysisServices), and

several messaging technologies, specificallyService Broker and Notification Services.

1993 - SQL Server 4.21 for Windows NT 1995 - SQL Server 6.0, codenamed SQL95 1996 - SQL Server 6.5, codenamed Hydra 1999 - SQL Server 7.0, codenamed Sphinx

Releases


1999 - SQL Server 7.0 OLAP, codenamedPlato

2000 - SQL Server 2000 32-bit, codenamedShiloh (version 8.0)

2003 - SQL Server 2000 64-bit, codenamedLiberty

2005 SQL Server 2005 codenamed Yukon

Releases Cont


2005 - SQL Server 2005, codenamed Yukon(version 9.0)



MS SQL Server uses a variant of SQLcalled T-SQL, or Transact-SQL, animplementation of SQL-92 with someextensions.

T-SQL mainly adds additional syntax for use

Description


y yin stored procedures, and affects the syntaxof transaction support. (Note that SQLstandards require Atomic, Consistent,Isolated, Durable or "ACID" transactions.)

MS SQL Server and Sybase/ASE bothcommunicate over networks using anapplication-level protocol called Tabular DataStream (TDS).

The TDS protocol has been implemented in

Description Cont


The TDS protocol has been implemented inorder to allow more kinds of clientapplications to communicate with MS SQLServer and Sybase databases.

MS SQL Server also supports OpenDatabase Connectivity (ODBC).

According to Microsoft, future versions of SQLServer aim to make data management self-tuning, self organizing, self maintaining

Future development


self maintaining with the introduction of SQL Server AlwaysOn technologies, to provide near-zerodowntime.



Microsoft also aims to intrinsically supportmany digital data formats, including pictures,audio, video and other multimedia data. Incurrent versions, such multimedia data canbe stored as BLOBs (binary large objects),but they are generic bitstreams Intrinsic

Future development Cont


but they are generic bitstreams. Intrinsicawareness of multimedia data will allowspecialized functions to be performed onthem.

Better support for unstructured and semi-structured data is planned as well.

What is Object Oriented Database? (OODB)

A database system that incorporates all the important object-oriented concepts.

Some additional features


Unique Object identifiers Persistent object handling

Advantages of OODBS Designer can specify the structure of objects and

their behavior (methods)

Better interaction with object-oriented languages such as Java and C++


Definition of complex and user-defined types

Encapsulation of operations and user-defined methods



Lack of Industry Standards

RDBMS Popularity

Object Oriented Databases Disadvantages.


RDBMS Popularity

Spatial Databases It had been state that approximately 75% to

80% of all the information contains somenotion of the location.

So Spatial database system give the


So, Spatial database system give theconcept of database that helps in keeping thetrack of objects in multidimensional space.

A spatial database is also known as a databasethat is used to store and querying data related tothe object in space like points, lines and polygonsetc.

Spatial Databases Cont


While we can see that most of the data layer candeals with various numeric and character datatypes in order to implements spatial databasessome additional functionalities needs to added inthe database to add-on some geometry relatedspatial data types.



A most common example for the spatial data we can see in the map of road, in which we can see various spatial objects along the 2-Dimension, some of these spatial objects are points, line and polygons etc. these objects some how can represents roads, cities, state boundaries etc.



A road map is a classic example of spatial information. The roads, cities, state boundaries reside on the piece of paper in 2-D format. A GIS is used to retrieve, store and manage the spatial data.

Types of Queries supported by spatial Databases:

1. Spatial Scope-Distance Query.2. Spatial Nearly Queries3. Joins Queries.



3. Joins Queries.

Multimedia Databases Multimedia Database System(MMDBS) are created

in order to cope up with the growth in the usage of huge volume of multimedia data that is used by various applications such as journalism software applications, e-retailing, entertainment and e-libraries etc.


libraries etc.

The multimedia data has the influence both directly as well as indirectly in the development of multimedia databases.



Multimedia data bases are design in the various similar manner that are highlighted by the classical DDBMSs to give ease of use and understandability to its user, along with the MMDBS provide some additional features to its user.

Multimedia Databases


These MMDBs are provide a frame work to store, process, retrieve, present and transmit variety of multimedia data-types in lot many formats multimedia database support more new features as compared to the traditional DBMSs.

Multimedia Databases Cont... Multimedia data characterize in images, video,

audio and text.

Moreover, MMDBSs are very necessary for the


y yefficient as well as effective management of largeamount of multimedia data.

Deductive Databases A deductive database is a database system that

can make deductions, these deductions are based on some rules and facts that are stored in the databases (deductive).


Prolog and Datalog are the languages that are mainly used to specifies rules, facts and queries in the deductive databases.



Deductive data bases are based on the desire ofcombining logic programming with the RDBMS tomade such a system that support powerfulcalculation and also system can give very fastresponse time and deals with large datasets.Deductive database systems are far more

Deductive Databases Cont


Deductive database systems are far more.

Expensive than a RDBMS system but economicalagainst logic programming systems.

Now a days, Deductive database systems arelargely used in academics as compare to industries,

Deductive Databases Cont


but lot many concepts of Deductive databasesystem are used in today's Relation Databasesystems to give support to various new SQLstandards.

Temporal Databases Temporal database are created to store the

temporal data, it means data that is dependent on time.

Temporal DBMS or TDBMS is created in order to


support the manipulation as well as maintenance of the temporal data.

TDBMS provide the Temporal data model (TDM) that comprises of TDDL (Temporal Data Definition Language) and TDML (Temporal Data Manipulation Language)



Temporal database objects are defined using TDDLwhile Temporal database are manipulated i.e.,update, delete and retrieve etc. with the help ofTDML.

Temporal Databases Cont


Further, it can be seen that some specific queriesrelated to the temporal data are very difficult toexpress in term of simple SQL query, whiletemporal DBMS give us a better support toimplements these specific queries, it may also bepossible to use SQL queries for these purpose butagain the performance factor is a big issue.

Short Questions Explain about the federated database give

any example ? What is Open database connectivity? Briefly describe the architecture of SQL

server?


server? Write some difference between

heterogeneous and homogenous DDBMS?

Long Questions Explain any one heterogeneous DDBMS ? What

are the problems that can occur in a heterogeneous DDBMS.

Write Short notes on the following :(a) Open Database Connectivity


(a) Open Database Connectivity(b) SQL Server Architecture

Discuss the loosely and tightly coupled architectures of parallel and distributed systems.

What is federated database system? Explain its features.



Long Questions Difference between homogenous DDBMS

and heterogeneous DDBMS ? Give one example in each case?

Explain client server database and peer to


Explain client server database and peer to peer architecture?

Explain reference architecture of federated database ?

References1. S. Ceri, G. Pelagatti, Distributed Database: Principles

and Systems, McGraw Hill, New York, 1985.2. M. Tamer Ozsu, Patrick Valduriez, Principles of

Distributed Databases System, Pearson, 2nd Ed., 2009.

3 Mario Piattini Advanced Database Technology and


3. Mario Piattini, Advanced Database Technology and Design, Artech House, UK, 2000.

4. Shivendra Goel, Divya Goel, Distributed Database Management System, Sun India Publications, 2009.

5. Chhanda Ray, Distributed Database System, Pearson, 2009.

Ddbms Unit 4

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