ISRO 2009 Answer Key and Solutions Computer Science Scientist Engineer

The ISRO Computer Science (CS) Scientist Engineer test held on April 26, 2009 (Sunday). Total questions were 80 and test duration were 90 Minutes. Here is the solution of paper according to me of set A.

• The Answer Key 2009 for Set A Non-Official by Me: Click here (By ISRO not available)
• For complete preparation for ISRO Computer Science visit my this article: Click Here 
• For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2016: Click here
• For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2015: Click here
• For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2014: Click here
• For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2013: Click here
• For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2011: Click here
• For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2008: Click here
• For ISRO Answer Key and Solutions Computer Science Scientist Engineer 2007: Click here

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70. A locked database file can be
(a) Accessed by only one user
(b) Modified by users with the correct password
(c) Used to hide sensitive information
(d) Updated by more than one user

Correct Answer: (a)

Explanation: File locking is a mechanism that restricts access to a computer file by allowing only one user or process access at any specific time.

Reference: http://edugrip.blogspot.in/2012/07/database-management-system-multiple.html

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71. Which of the following contains complete record of all activity that affected the contents of a database during a certain period of time?
(a) Transaction log
(b) Query languages
(c) Report writer
(d) Data manipulation language

Correct Answer: (a)

Explanation: A transaction log (also transaction journal, database log, binary log or audit trail) is a history of actions executed by a database management system to guarantee ACID properties over crashes or hardware failures. Physically, a log is a file listing changes to the database, stored in a stable storage format.

Reference: https://en.wikipedia.org/wiki/Transaction_log

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72. Purpose of 'Foreign Key' in a table is to ensure
(a) Null Integrity
(b) Referential Integrity
(c) Domain Integrity
(d) Null & Domain Integrity

Correct Answer: (b)

Explanation: A foreign key is a column (or columns) that references a column (most often the primary key) of another table. The purpose of the foreign key is to ensure referential integrity of the data.

Reference: https://www.1keydata.com/sql/sql-foreign-key.html

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73. Which of the following scenarios may lead to an irrecoverable error in a database system?
(A) A transaction writes a data item after it is read by an uncommitted transaction
(B) A transaction reads a data item after it is read by an uncommitted transaction
(C) A transaction reads a data item after it is written by a committed transaction
(D) A transaction reads a data item after it is written by an uncommitted transaction

Correct Answer: (d)

Explanation:

• In option D, there is dirty read. In case if transaction reading uncommited data commits and that uncommited transaction fails then irrecoverable error occurs.
• In option B, there is no issue. Both transaction are reading data.
• In option C, it is normal. Someone reading a item after committed write by someone.
• In option A, it is recoverable. Here write committed after uncommitted read by someone, if again after read done in same uncommitted transaction then there will be phantom error only.

Note: Same question had asked in GATE 2003 CS exam.
Reference: http://gateoverflow.in/919/gate2003_29

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