Question

What are the design issues of Concurrency in programming? Briefly discuss.

Answer 1

Explanation:

There are the following design issues of Concurrency which are explained below

(i). Temporary Update Problem

(ii). Incorrect Summary Problem

(iii). Lost Update Problem

(iv). Unrepeatable Read Problem

(v). Phantom Read Problem 

(i). Temporary Update Problem

A temporary update problem occurs when one transaction updates an item and fails. But the updated item is used by another 

transaction before the item is changed or reverted back to its last value.

(ii). Incorrect Summary Problem

Consider a situation, where one transaction is applying the aggregate function on some records while another transaction is updating these records. The aggregate function may calculate some values before the values have been updated and others after they are updated.

(iii). Lost Update Problem

In the lost update problem, an update done to a data item by a transaction is lost as it is overwritten by the update done by another transaction.

(iv). Unrepeatable Read Problem

The unrepeatable problem occurs when two or more read operations of the same transaction read different values of the same 

variable.

(v). Phantom Read Problem 

The phantom read problem occurs when a transaction reads a variable once but when it tries to read that same variable again, an error occurs saying that the variable does not exist.