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Wait-die" scheme: The idea is based on non-preventive method. It is based on a simple rule:
If Ti requests a database resource that is held by Tj
then if Ti has a smaller timestamp than that of Tj
it is permitted to wait;
else Ti aborts.
A timestamp may loosely be described as the system generated sequence number that is unique for every transaction. Therefore, a smaller timestamp means an older transaction. For example, suppose that 3 transactions T1, T2 and T3 were generated in that series, then if T1requests for a data item which is presently held by transaction T2, it is permitted to wait as it has a smaller time stamping than that of T1. Though, if T3 requests for a data item which is presently held by transaction T2, then T3 is rolled back (die).
Figure: Wait-die Scheme of Deadlock prevention
Explain trivial dependency? Functional dependency of the form α ->β. is trivial if α C β. Trivial functional dependencies are satisfied by all the relations.
Write an sql statement to find what is the percentage of home policies which are from the state of Arizona out of all Home policies by Policy Value.
Higher Normal Forms Is there more normal forms beyond BCNF? Yes, though, these normal forms are not based on the concept of functional dependence. More normalisation is needed if
What is completeness constraint on generalization? Define the variation between total and partial design constraint. Give an example each. Ans: Completeness Constraints
#question benefits and limitations of data models..
WHAT IS DATABASE TECHNOLOGIES
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I want Database Of United Kingdom with Criteria of:\r\n\r\n1). Name, Number, City, State, Postal Code, Address, Email id, DOB.\r\n\r\n2). Unsecure Debts only adds Credit Card Payme
Question: (a) With the help of a diagram, explain the TOGAF framework for enterprise architectures. (b) Where would you position enterprise architectures in an enterpri
explain cascading rollback
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