Project Management

What is the advantage of concurrency control?

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Wiki User
September 13, 2005 5:02AM

By having concurrency control you avoid dirty writes (or

inconsistent data). It is like your traffic signal - allows one set

of users (drivers) to pass through at a time. In computer terms, if

a user wants to update some data then the following steps are

taken: (a) the data is fetched along with the timestamp (the date,

time when it was last modified) (b) the data is modified by the

user who then submits the data for update / storage in the system

(c) the system verifies the original timestamp with the current

timestamp. (i) If both are same, the new data (including the new

timestamp) is updated/stored in the system. (ii) If they are

different, then obviously the data had changed between the time it

was fetched and now - meaning that someone else had updated in the

meanwhile. The system typically informs the user that the data had

been modified by a different user and asks him/her to submit the

modifications once again. The system would implicitly do step (a)

above allowing the user to start from step (b) onwards.


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