We are given the following transaction schedule, where A,B,C are the addresses of the records in the database and T1 and T2 are the transactions. T1 R(A) W(A) R(B) W(B) R(C) W(C) COMMIT T2 R(C) R(B) W(B) a) Show that using strict two-phase locking leads to complications b) For example a, draw a »waits-for<< graph c) Resolve the problems in example a, using the "Wound-Wait" protocol R(A) W(A) W(C) COMMIT

We are given the following transaction schedule, where A,B,C are the addresses of the records in the database and T1 and T2 are the transactions. T1 R(A) W(A) R(B) W(B) R(C) W(C) COMMIT T2 R(C) R(B) W(B) a) Show that using strict two-phase locking leads to complications b) For example a, draw a »waits-for<< graph c) Resolve the problems in example a, using the "Wound-Wait" protocol R(A) W(A) W(C) COMMIT

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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(1) How to prove H using given rules and facts: Rules: Rule 1 A ∧ B → C Rule 2 A → D Rule 3 C ∧ D → E Rule 4 B ∧ E ∧ F → G Rule 5 A ∧ E → H Facts: Fact 1 A Fact 2 B Fact 3 F Hint: The goal is to prove H. First let us use forward chaining. As the conflict resolution strategy, one will fire rules in the order they appear in the database. Let us fire Rule 1, which means to add C to the fact database. Next, Rule 2 is fired, meaning we add D to our fact database. We now have the facts A, B, C, D, F, but we have not yet reached our goal, which is H. Please list the rules to be triggered to add fact H to the database. Now consider using backward chaining. Does backward chaining use fewer rules?
Select from below ALL statements that are true. Select one or more: a. Adding locking and unlocking statements (in arbitrary ways) to transactions is sufficient to assure database consistency in concurrent schedules. b. A conflict serializable schedule assures database consistency. c. The "B" in "B+-tree" stands for "Binary". d. The search key field/attribute of a primary index for a table does NOT have to be the primary key of the table. e. If an index is a sparse index, it MUST BE a primary index. f. It is a good idea to allow ONLY SERIAL schedules because they guarantee database consistency.
Suppose we have a record file constructed according to the SimpleDB specificapoints) Suppose we have a record file constructed according to the SimpleDB specifications. That is, the block size is 400 bytes, an integer occupies 4 bytes, a string requires an integer length plus one byte per character, and each slot of a record page has an integer INUSE/EMPTY flag; records do not span multiple pages. For each of the tables in the sample database (and assuming there are many records in each table, not just the given sample data), determine how many records will fit per block (be sure to show your calculations). Is there any wasted space in any of the blocks?tions. That is, the block size is 400 bytes, an integer occupies 4 bytes, a string requires an integer length plus one byte per character, and each slot of a record page has an integer INUSE/EMPTY flag; records do not span multiple pages. For each of the tables in the sample database (and assuming there are many records in each table,…
Suppose that you are running manually the Apriori algorithm to find the frequent itemsets in a given transaction database. Currently, you have determined the candidate set of 2-itemsets, C2, and the corresponding support count of each candidate 2-itemset. Assuming that the minimum support count is 3, which candidate 2-itemsets in C₂ would be frequent 2- itemsets? Select all that apply. {I1, I2), support count = 1 {I₁, I3}, support count 3 {I₁, I4}, support count = 3 {I2, I3), support count {I2, I4}, support count = 1 {I3, I4}, support count = 4 = 2
2. DEL Transactions: The following transaction schedule is given. A,B,C are the addresses of the records in the database and T1, T2 and T3 are the transactions. T1 R(A)W(A) R(C) R(B)W(B)C T2 T3 R(B) W(B) R(C) R(B)W(B) R(A) с a) Show an example of a strict 2PL implementation that leads to a deadlock b) For a) draw a >>wait-for<< graph c) Avoid the previously drawn deadlock with a wait-die<< policy d) Give an example of another schedule that would be conflict-equivalent to the given schedule of transactions W(A)C
2. CHAPTER TRANSACTION MANAGEMENT Consider the case of immediate database approach and assume that, after a crash, the log contains the following records: Transaction Object Old Value New Value LSN L001 T1 (starts) P. 400 500 LO02 T1 300 400 LO03 T1 L004 T2 (starts) LO05 T1( commits) LO06 T3 (starts) R. 100 200 LO07 T2 700 800 LO08 T3 LO09 T4 (starts) L010 T3 (commits) T4 T. 800 900 L011 i) Which transaction(s) will be redone during recovery process? ii) Which transaction(s) will be undone during recovery process? ii) What will be the value of data item 'P' and 'T' after the recovery?
Using linear hashing to insert the given values in the order provided with the hash function hi(K) = K mod 2i . Display how the file grows and the hash functions changes as the records are inserted. Draw the diagrams showing the loading of the data into buckets, overflows, and splits. Also, calculate the average number of block accesses for a random retrieval on the given records. Given records are 2369, 3760, 4692, 4871, 5659, 1821, 1074, 7115, 1620, 2428, 3943, 4750, 6975, 4981 and 9208.
Consider the following scenario: there is only place for one extra student in the class that two students wish to enrol in. What is it about a database that stops both of these students from claiming the last open seat?
2. For a transaction database such as follows, there exists a hierarchy on categories of items: TID Items apple, lamb, rice apple, sugar, rice beef, rice, apple apple, pear, sugar rice 100 200 Fruit Food 300 аpple рear meat rice sugar 400 500 lamb beef apple, pear beef, rice 600 700 (a) Find all frequent itemsets using the basic algorithm given in the lecture (minimum support = 3 transactions). (b) Generate all generalised association rules (minimum confidence = 90%)
Check the given schedule for serializability: T1 T2 T3 T4 R(X) W(X) Commit W(X) Commit W(Y) R(Z) Commit R(X) R(Y) Commit All the methods for checking the serializability should be discussed with well drawn schedules and diagrams, if any.
Consider the following two transactions: T1-R(B), W(B), R(C), R(A) T2-R(B). W(B) Say that sharing lock, exclusive lock, and unlock actions are inserted by the scheduler, resulting in the following annotated transactions: T1= X(B), R(B), W(B), S(C), R(C), S(A), U(B), R(A), U(C), U(A) T2-X(B), R(B), W(B), U(B) Cascading rollback is not possible for the above schedule. True False
Suppose we (incorrectly) modify the recovery algorithm of Section 19.4 tonote log actions taken during transaction rollback. When recovering from asystem crash, transactions that were rolled back earlier would then be includedin undo-list and rolled back again. Give an example to show how actions takenduring the undo phase of recovery could result in an incorrect database state.(Hint: Consider a data item updated by an aborted transaction and then updatedby a transaction that commits.)