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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 all the replicas of the relation require to be updated at the similar time, resulting in increased overheads. For instance, in a banking system, if account information is replicated at several sites, it is essential that the balance in a particular account should be the similar at all sites.
The problem of controlling concurrent updates by various transactions to replicated data is more difficult than the centralised approach of concurrency control. The management of replicas of relation can be simplified by deciding one of the replicas as the primary copy. For instance, in a banking system, the primary copy of an account may be the site at which the account has been opened. Likewise, in an airline reservation system, the primary copy of the flight may be related with the site at which the flight originates.
Example -GRANT CREATE SESSION TO MCA12; (This command gives system level permission on creating a session - not portable) GRANT SELECT ON EMP TO MCA12; (Object level permi
Explain controlled redundancy? Controlled redundancy : The replication of data within the data warehouse for the purposes of improved data access or understand ability.
Explain ODBC? ODBC - Open DataBase Connectivity (ODBC) enable the integration of SQL along with a general-reasons programming language.
explain at least five widly used case tools
Show a centralised schema to support the operation of the system you have chosen, including in particular: the product catalogue; the outlets and respective stocks; customer record
Deadlock And Its Prevention: As seen earlier, though two phase locking protocol handles the trouble of serialisability, but it causes some troubles also. For instance, consider th
10A.53 Code an Oracle Database trigger to enforce the constraint that an employee can never change his or her department. 10A.54 Code an Oracle Database trigger to allow the
The indices are accumulated in the index files. The data is accumulated in the data files. Indices give fast access to data items. For example, a book database may be managed in th
Special comparison operator used in where Clause a. between. ...and...It gives range among two values (inclusive) Example: SELECT ENAME, SAL FROM EMP WHERE SAL BETWE
What are partial, alternate,, artificial, compound and natural key? Partial Key: It is a set of attributes that can uniquely recognize weak entities and that are related to s
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