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Transactions And Concurrency Management
Introduction
One of the main benefits of storing data in an integrated repository or a database is to permit sharing of it between multiple users. Various users access the database or perform transactions at the similar time. What if a user's transactions try to access a data item that is being used /modified by another transaction? This unit attempts to give details on how concurrent transactions are implemented under the control of DBMS. Though, in order to describe the concurrent transactions, first we must explain the term transaction.
Concurrent implementation of user programs is essential for good performance of DBMS, as concurrent running of various user programs keeps utilizing CPU time efficiently, as disk accesses are frequent and are relatively slow in case of DBMS. Also, a user's program may carry out a lot of operations on the data returned from DB, but DBMS is only concerned about what data is being written from / read / into the database.
Suppose that in an organisation, an employee may do different roles in dissimilar projects. Say, RAM is doing coding in one project and doing designing in another. Suppose that the
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Describe Parameteric end users? Parametric end users might be given update access, but are commonly not permitted to change the structure of data.
Consistency error : These errors happen due to the inconsistent state of database caused may be due to wrong implementation of commands or in case of a transaction abort. To overc
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