DBMS Miscellaneous : MCQs & PYQs with Explanation

Option A

RAID (Redundant Array of Independent Disks) is a storage technology that combines multiple physical disks into a single logical unit to improve performance and reliability (fault tolerance). Key characteristics of RAID include:

• Data Striping: Distributing data across multiple disks to improve read/write performance.
• Redundancy/Parity: Using extra disk space to store parity or mirrored data for fault tolerance.
• Logical View: The OS treats the RAID array as a single logical drive, even though it consists of multiple physical drives.

Option B

A Work File is a temporary file created by an information system to perform a specific or single task. It is used to hold intermediate data during processing and is usually discarded after the task is completed.

Option A

RAID (Redundant Array of Independent Disks) is used to improve data reliability and performance. Different RAID levels use different techniques like mirroring and parity.

• Parity is a method used to recover data if a disk fails.
• Some RAID levels use parity, while others do not.

The RAID 1 uses mirroring, not parity. Data is duplicated on two or more disks. If one disk fails, the same data is available on the other disk.

Option A

QBE (Query By Example) is a graphical query language where users specify queries by filling example values in tables. The condition box in QBE is specifically used to define constraints or conditions on domain variables, such as comparisons, ranges, or logical conditions.

• The SQL uses the WHERE clause, not a condition box.

Option A

The DUAL table is a special one-row, one-column table provided by Oracle. It is commonly used to evaluate expressions, call functions, or display system values without referencing any user table. 
The owner of the DUAL table is SYS, which is the default system schema in Oracle.

Option C

According to the Bell-LaPadula security model, a subject S is permitted to write to an object O only if the security classification of the subject satisfies the condition:
class(S)≤class(O)
This is known as the "No Write Down" or Star (*) Property rule, which prevents a subject from writing information to a lower security level object, thereby preventing potential information leakage from higher classified data to lower classification levels.

Option C

A fourth-generation language (4GL) is a non-procedural language that allows users to specify what result is required, not how to compute it.
SQL fits this definition because users write queries to describe the desired data, and the DBMS decides the execution steps.

Option D

Database security is maintained using:

• Data Encryption protects data from unauthorized access by converting it into unreadable form.
• Passwords authenticate users before allowing access to the database.
• Granting Privileges controls what actions a user can perform.

Option A

In DBMS Query Processing, data is accessed through different levels of operations. The lowest level operation is the one that directly reads data from the storage (disk).
A File Scan is the basic operation where the system reads records sequentially from a file to find the required data.
Whenever a query is executed, if no index is available, the DBMS performs a file scan to access records. Since it directly interacts with the stored data, it is considered the lowest level operator.

• File Manipulation refers to higher-level operations like insert, delete, update.
• File Organization describes how data is stored, not how it is accessed.

Option B

A trigger is a stored program that automatically executes when a specific event occurs on a table or view. 
In Oracle DBMS, triggers are written using PL/SQL, which extends SQL with procedural features like variables, conditions, and loops.

Option A

Performance benchmarks are a set of standard tasks or workloads used to measure and quantify the performance of a system, such as response time, throughput, or resource usage.

• Qualify means describe quality, not measure performance numerically.

Option C

QBE (Query By Example) uses a two-dimensional, tabular syntax where users specify queries by filling values into table-like forms. 
Rows and columns are used to represent conditions and data, making it easy and visual.

Option C

Oracle is primarily an Object–Relational Database Management System (ORDBMS). It is based on the relational model but also supports object-oriented features such as user-defined types, inheritance, and methods.

Option D

Authorization defines the permissions granted to a user regarding database operations.

• Read authorization allows a user to view data by using SELECT statement.
• Insert authorization allows adding new records by using INSERT statement.
• Update authorization allows modifying existing data by using UPDATE statement.

Option A

A Transactional File stores day-to-day business operations such as sales, purchases, payments, or receipts. These records are created frequently and change regularly as business activities occur.

• Master File stores relatively permanent data like customer details or employee records, not daily transactions.
• Work File is a temporary file used during processing and does not permanently store business transactions.