Chapter 7, Problem 1RQ

To determine

Hidden tasks performed by DBMS when users update and retrieve data.

Explanation of Solution

A DBMS is of no use to any user if it's not capable of providing some functions. Updation and retrieval are the fundamental job of a DBMS. Thus, a DBMS must provide to its users the ability to perform same. These tasks are solely the responsibility of a DBMS and a user needs not be aware of them.

The general steps followed in almost all operations are in diagram below:

An operation contains instructions given by users and some tasks that are performed at the backend.

The difference usually occurs at step 2 and 3 where more than one sub operations might be needed to complete the task.

An updation operation can be performed by a user in the following way: by adding a new record, changing an existing records or it's deletion. All these consist of some instructions given by user and some task performed by DBMS.

Updation:

1. adding new records:

User enters an item and requests the DBMS to add a new item into database.

Following tasks are performed by DBMS following the request:

• It checks whether the records already exist in Database
• If not, it creates a new record and adds it to the database.
• Informs the user that the operation is complete, and the record is now a part of the database.

2. Changing a record:

User requests the DBMS to change an item from the database.

Following tasks are performed by DBMS following the request:

• It reads the data from database that needs to be changed.
• It displays the current data to user so that new value can be provided for changing.
• It changes the value as soon as new value is provided.

3. Deleting a record:

User requests the DBMS to delete an item from the database.

Following tasks are performed by DBMS following the request:

• It reads the data from database that needs to be deleted.
• It displays the current data to user so that user is able to see what will be deleted.
• It deletes the value as soon as user confirms the deletion action.

Retrieval:

A user is capable of reading a value from database. Following are the steps performed by DBMS to complete the operation:

• It finds and reads the record from database
• It displays the record to user

Thus, an operation consists of both the task done by a user and the tasks performed by a user. The DBMs is fully capable of performing these sub tasks at backend without the user being aware of it.