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Hey guys! May i know what is the possible way to achive 22 marks for these questions?

Answers

  • cormaco
    cormaco Member Posts: 1,720 Bronze Crown

    Please observe the Posting Etiquette:

    Community Posting Etiquette - oracle-tech

    Don't post exam or certification questions for other users to answer


    This is considered cheating and is not permitted. Your account may be suspended or banned for this type of activity.

  • User_LM22Y
    User_LM22Y Member Posts: 12 Green Ribbon

    But this is just a tutorial questions within my subject!

  • JohnWatson2
    JohnWatson2 Member Posts: 4,327 Silver Crown

    You could start by discussing each step. Begin with the first: "begin-trans". What does that mean, and how would you implement it?

  • User_LM22Y
    User_LM22Y Member Posts: 12 Green Ribbon

    Good Day John Watson! The "begin-trans" is stating that the transaction starts there.

    Here is my answer can you check my first question answer?

    pls correct me if im wrong,

    My Answer:

    Lost-Update Problem

    As for the transaction T1, the value A is being read at time t1 which is 160 and value B is being read at time t2 which is 60. During time t2, Transaction T2 begins, and value B is being read as well which is known as a dirty-read. Followed by time t4, the value B has been calculated in Transaction 1 and on time t6, value B has been partially committed which is 120 meanwhile, in Transaction T2 time t5, value B has been calculated as well which now holds 120 and is being partially committed as well. Lastly, value B which is 120 has been committed in Transaction 1 on time t7 and later followed by value B which is 120, committed in Transaction 2 on time t11. This is when Lost-Update problem occurs whereby the value B on Transaction 1 is overwritten by value B on Transaction T2.


    Versioning Approach --> still unsure sir, hope to have guidance from you!

  • JohnWatson2
    JohnWatson2 Member Posts: 4,327 Silver Crown

    If I were your teacher, I would be asking whether you understand why the problem could occur. That would mean going back to "begin-trans". What is it doing? What level of isolation (if any) is it implementing? What sort of locks would be applied? You could refer to the commonly used isolation levels, such as "serializable" or "read uncommitted".

    One particular point: your term "partially committed" would cause Ted Codd to rollback in his grave.

    User_LM22Y
  • User_LM22Y
    User_LM22Y Member Posts: 12 Green Ribbon
    edited Sep 27, 2021 7:07PM

    U meant why lost-update occurred? Isnt it because of the value B of Transaction 1 being overwritten by value B of Transaction T2?


    And the begin-trans is stating the transaction begins there isnt it ? Im really not good at this im sorry