The document discusses the purpose of database administration, which involves managing access to data by authorizing or de-authorizing users. It explains concurrency control as a method to ensure multiple transactions can safely access database objects, maintaining consistency. Additionally, it illustrates the lost update problem through an example where one transaction's update is overwritten by another, resulting in a loss of the original update.

1. What is the purpose of database administration?
2. What is the purpose of concurrency control?
3. Give an different example of the lost update problem in Lecture slide (Chapter 6-15)
4. Explain two-phase locking.
5. Explain the meaning of the expression of ACID transaction.
Solution
1. What is the purpose of database administration?
Data administration is the concept of managing people and their rights on how to access the data
and to which level of granularity is the different people/designations are allowed to access the
data base. Its just authorizing and de-authorizing people on how to access the data.
2. Purpose of concurrency control?
Concurrency control is allowing more than one transaction to access the object in a safe and
secure way such that the database is consistent at the end of multiple transactions. If concurrency
control not applied properly, either the transactions should be performed serially, or the
concurrent transactions may make the database inconsistent.
3. Give an different example of the lost update problem in Lecture slide (Chapter 6-15)
Lost update is the concept of one update done by a transaction is lost, just because the data is
read by other transaction before the update, and is written after the update.
Consider a scenario:
T1: Read A (Assume A = 50)
T2: Read A (Assume A = 50)
T2: Update A (Assume A is increased by 10)
T2: Write A (Now A = 60)
T1: Update A (Assume A is decreased by 10 )
T1: Write A (Now A = 40)
Here the update done by Transaction T2 is lost.