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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 data abstraction? Data abstraction Data abstraction is a methodology in which enables us to isolate how a compound data object is utilized from the details of how it is
Example : Create a sequence named SEQSS that starts at 105, has a step of 1 and can take maximum value as 2000. CREATE SEQUENCE SEQSS START WITH 105 INCREMENT BY 1 MAX VA
Assigning Responsibility for Operation Many operations might have obvious target objects, but some of these operations could be used at numerous places in an algorithm, by one
Benefits and limitations
What is a block and a block number? A block is a contiguous sequence of sectors from a single track of one platter. Every request specifies the address on the disk to be refere
SET concept is used in which type of modelling? SET concept is used in Network Model.
What is an object design? Object design is a very interactive method, which decides the relationship among objects, classifies operations on classes, determines overall system
Entities Let us first be aware of the question: What are entities? An entity is an object of concern used to show the things in the actual world, e.g., table, car, bo
Assume that you are responsible for selecting a new DBMS product for Sohar Hospital
Implementation of association as an object Implement as a separate association object, independent of either class, as in Figure. An association object is a group of pairs
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