The document discusses the key functions of distributed database management systems including keeping track of data distribution, processing distributed queries, managing replicated data, distributed recovery from failures, security across sites, distributed directory management, and distributed transaction management. It also classifies DDBMS as either homogeneous where all sites use the same DBMS or heterogeneous where sites may use different DBMS products requiring translations. The document describes how transaction transparency ensures integrity and consistency when transactions update data across multiple connected computers in a distributed database.

1. Tutorial 7
a)
Keepingtrackof data –
The basic functionof DDBMS is to keeptrackof the data distribution,fragmentationandreplication
by expandingthe DDBMScatalog.
DistributedQueryProcessing –
The basic functionof DDBMS is basicallyits abilitytoaccessremote sitesandtotransmitsqueries
and data amongthe varioussitesviaa communicationnetwork.
ReplicatedDataManagement –
The basic functionof DDBMS is basicallytodecide whichcopyof a replicateddataitemtoaccessand
to maintainthe consistencyof copiesof replicateddataitems.
DistributedDatabase Recovery –
The abilitytorecoverfromthe individual sitecrashesandfromnew typesof failuressuchasfailure
of communicationlinks.
Security –
The basic functionof DDBMS is to execute DistributedTransactionwithpropermanagementof the
securityof the data and the authorization/accessprivilege of users.
DistributedDirectoryManagement –
A directorybasicallycontainsinformationaboutdatainthe database.The directory maybe global
for the entire DDB,or local for eachsite.The placementanddistributionof the directorymayhave
designandpolicyissues.
DistributedTransactionManagement –
The basic functionof DDBMS is itsabilitytodevise executionstrategiesfor queriesandtransaction
that accessdata from more than one site andto synchronize the accesstodistributeddataand
basicallytomaintainthe integrityof the complete database.
b)
A DDBMS may be classifiedashomogeneousorheterogeneous.Ina homogeneoussystem,all sites
use the same DBMS product.In a heterogeneoussystem, sitesmayrundifferentDBMSproducts,
whichneednotbe basedon the same underlyingdatamodel,andsothe systemmaybe composed
of relational,network,hierarchical andobject-orientedDBMSs.

2. Homogeneoussystemsare mucheasiertodesignandmanage.Thisapproachprovidesincremental
growth,makingthe additionof a newsite tothe DDBMS easy,andallowsincreasedperformance by
exploitingthe parallel processingcapability of multiple sites.
Heterogeneoussystemusuallyresultwhenindividual siteshave implementedtheirowndatabase
and integrationisconsideredatalaterstage.In a heterogeneoussystem,translationsare required
to allowcommunicationbetweendifferent DBMSs.To provide DBMStransparency,usersmustbe
able to make requestsinthe language of the DBMS at theirlocal site.The systemthenhasthe task
of locatingthe dataand performinganynecessarytranslation.Datamaybe requiredfromanother
site that mayhave:
• Differenthardware;
• DifferentDBMSproducts;
• Differenthardware anddifferentDBMSproducts
If the hardware isdifferentbutthe DBMS productsare the same,the translationisstraightforward,
involvingthe change of codesandword lengths.If the DBMS productsare different,the translation
iscomplicated,involvingthe mappingof the datastructure inone data model to the equivalentdata
structuresinanotherdata model.Forexample,relationsinthe relational datamodel are mappedto
recordsand setsinthe networkmodel.Itisalsonecessarytotranslate the querylanguage used(for
example,SQLSELECTstatementsare mappedtothe networkFINDand GET statements).If boththe
hardware and software are different,thenthese twotypesof translationare required.Thismakes
the processingextremelycomplex.
The typical solutionuse bysome relationalsystemsthatare partof a heterogeneousDDBMSisto
use gateways,whichconvertthe language andmodel of eachdifferentDBMSinto the language and
model of the relational system.
c)
Transactiontransparencyisa DDBMS propertythatensuresthatdatabase transactionswill maintain
the distributeddatabase'sintegrityandconsistency.RememberthataDDBMS database transaction
can update data storedinmany differentcomputersconnectedinanetwork.

3. Part b
a)
Step-1:
Breakingthe groupof Columnstocreate 1st normalizationform.
Item(ItemNum,Description,OnHand,Category,Price,OrderNum, OrderDate,CustomerNum,
CustomerName, RepNum,LastName,FirstName,NumOrdered,QuotedPrice)
Step-2:
Convertingintothe 2ndnormalizationform.
Identifyingthe primarykeysforeachsubset;
(ItemNum,
(OrderNum,
(CustomerNum,
(RepNum,
Regroupingthe Columnsasperdependencies;
(ItemNum, Description,Category,OnHand,Price)
(OrderNum,OrderDate,CustomerNum,CustomerName,RepNum, NumOrdered,QuotedPrice)
(CustomerNum,CustomerName)
(RepNum,LastName,FirstName)
Assigningthe namesforthe newlyassignedtables;
Item(ItemNum,Description, Category,OnHand,Price)
Orders(OrderNum,OrderDate,CustomerNum,CustomerName,RepNum, NumOrdered,
QuotedPrice)
Customer(CustomerNum, CustomerName)
Rep(RepNum,LastName,FirstName)
Step3:
Convertingtothe 3rd normalizationformandcreatinga new table calledOrderlinewiththe
dependentrows:(OrderNum,ItemNum, NumOrdered,QuotedPrice).Sothe final contentwouldbe;
Orderline (OrderNum,ItemNum,NumOrdered,QuotedPrice)
Step4:

4. Namingthese tablesandputthe entire collectiontogether,givingthe following:
Item(ItemNum,Description,Category,OnHand,Price)
Orders(OrderNum,OrderDate,CustomerNum,CustomerName,RepNum, NumOrdered,
QuotedPrice)
Customer(CustomerNum, CustomerName)
Rep(RepNum,LastName,FirstName)
Orderline (OrderNum,ItemNum, NumOrdered,QuotedPrice)
Functional dependenciesare;
Orderstable:
Orderline table dependsonOrderstable forthe columns(OrderNum,NumOrdered,QuotedPrice)
and Itemtable forthe columnItemNum.