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vertical fragmentation-vertical fragmentation groups together only those attributes in a relation that are used jointly by various important
horizontal fragmentation-horizontal fragmentation groups together the tuples in a relation that are collectively used by the main transactions a
security data not needed by local applications is not stored at the site therefore no unnecessary security violations may existbut how can we carry
parallelism of transaction execution a transaction can be divided into various sub-queries that can operate on fragments in parallel this enhances
increases efficiency data is stored close to most often used site therefore retrieval would be faster also data that is not required by local
use of partial data by applications in common applications work with views rather than whole relations thus it may be more appropriate to work
data fragmentationfragmentation includes decomposing the data in relation to non-overlapping component relationswhy do we require fragmenting a
selective replication this is a combination of generating small fragments of relation and replicating them rather than a entire relation the data
complete replication it implies maintaining of a whole copy of the database at every site thus the reliability amp availability and performance for
increased overheads on update on the drawbacks side it will need the system to ensure that all replicas of a relation are consistent this shows that
increased parallelism since the replicated date has several copies a query can be distributed or can be answered from the smallest loaded site also
availability a site having the copy of a replicated relation fails even then the relation may be found in another site therefore the system may carry
data replicationif a relation r has its copies kept at two or more sites then it is considered replicatedbut why do we replicate a relationthere are
fragmentation it is definite as partitioning of a relation into various fragmentsevery fragment can be stored at a dissimilar
replication it is definite as a copy of a relation every replica is stored at a dissimilar site the alternative to replication is to store only
design of distributed databases the distributed databases are mainly relational at local level so a local database schema is the similar as that of a
mysql statements for extending the database to incorporate new facilitiesdeliverables for submissionyou must submit the following deliverables in the
now that she understands more about the benefits of databases the play-scheme manager would like to extend the play-scheme database to include data
a database named yourusernamefma has been set up for you to use for this assignment for the fma you must create the required tables and run the
1 create the tables for the play-scheme database as specified in the tma2 enter the data as given in the spreadsheet3 create queries to retrieve
1suppose you are given a dataset that consists of a random sample of tasters on which the following variables were obtainedy zpref taste preference
lack of standards and experience the lack of standards has considerably limited the potential of distributed dbmss as well there are no tools or
security in a centralised system access to the data can be simply controlled though in a distributed dbms not only does access to replicated data
complexity a distributed dbms that is available reliable and secure is inherently more difficult than a centralised dbms though adequate data
greater potential for bugs since the sites of a distributed system operate simultaneously it is more complex to ensure the correctness of algorithms