1 What is the purpose of transaction isolated level 2 Explai

1) What is the purpose of transaction isolated level?

2) Explain the difference between an explicit lock and implicit lock.

3). Explain the relationships of users, groups, permission, and objects for a generic database security system.

4). Define the terms roll-back and roll-forward.

5) Why is it important to write to a log before changing the database value?

Solution

1.The purpose of the transaction isolated level is to restrict the access to the resources or the data to restrict inconsistencies that will be caused due to multiple access permission to various users. Transaction isolation level establishes lock over the data.

2.Implicit locks are the locks that are established over the data automatically by the DBMS where as the locks which are issued by the user such as developer to the data then it is known as explicit lock. Explicit lock helps you to reserve the resources that are required in advance by acquiring a lock over the data.

3. User can be part of one or more groups. Groups may contain 1 or multiple people. Object is an element of a database such as tables. Permissions are used to associate the users, groups and objects. like which user has access to which objects. It is more like restricting the access to the data for security reasons.

4.Roll-back is an action of taking the transaction to the beginning state. This can be applied only before the transaction is commited but not after that. Roll-forward is an action of redoing the transaction and applying the changes made to the trasaction after the commit.

5. Writing log helps to retrieve the data if any system crash takes place. for example, if the system crashes between the data is applied and logged, there will be inconsistency in the data as the changes cannot be applied due to the system crash.