Database Systems: Design, Implementation, & Management
12th Edition
ISBN: 9781305627482
Author: Carlos Coronel, Steven Morris
Publisher: Cengage Learning
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Chapter 10, Problem 11P
Program Plan Intro
Pessimistic locking:
It is one of the locking methods in concurrency control. The lock exists in the transaction until the transaction gets committed or rolled back.
Two-phase locking protocol:
It defined the serializability of the transaction but not prevent deadlocks. The process of locking and unlocking can be done using two phases in this protocol. They are: Growing phase and shrinking phase.
Growing phase:
New lock can be occurred on the transaction without unlocking the data items. The data items are locked in this phase.
Shrinking phase:
This phase used to release all transaction but not provide new lock on the transaction.
Row-level lock granularity:
This row-level locking process used to lock the single row in the table. It is used to improve the availability of data and involving in transaction conflict.
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Explain the phenomena of phantoms. Why is it possible that this occurrence, despite the usage of the two-phase locking scheme, leads to improper concurrent execution?
What does it mean for a database to be in a stable state? While the database management system may give a symbolic meaning for a transaction, there is no assurance that it faithfully captures the underlying real-world event. What consequences may be expected if this ban were implemented? Explain your point using an illustration. Should we take at face value the apparent meaning of the phrase "serializable transactions"?
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Chapter 10 Solutions
Database Systems: Design, Implementation, & Management
Ch. 10 - Prob. 1RQCh. 10 - Prob. 2RQCh. 10 - Prob. 3RQCh. 10 - Prob. 4RQCh. 10 - Prob. 5RQCh. 10 - Prob. 6RQCh. 10 - Prob. 7RQCh. 10 - Prob. 8RQCh. 10 - Prob. 9RQCh. 10 - Prob. 10RQ
Ch. 10 - Prob. 11RQCh. 10 - Prob. 12RQCh. 10 - Prob. 13RQCh. 10 - Prob. 14RQCh. 10 - Prob. 15RQCh. 10 - Prob. 16RQCh. 10 - Prob. 17RQCh. 10 - Prob. 1PCh. 10 - Prob. 2PCh. 10 - Prob. 3PCh. 10 - Prob. 4PCh. 10 - Prob. 5PCh. 10 - Prob. 6PCh. 10 - Prob. 7PCh. 10 - Prob. 8PCh. 10 - Prob. 9PCh. 10 - Prob. 10PCh. 10 - Prob. 11P
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- When the application of an optimistic approach to concurrency control is implemented, it is frequently observed that transactions experience prolonged durations for completion. Explain?arrow_forwardExplain the concept of conflict-avoidance and its application in concurrency control, with reference to techniques like Strict Two-Phase Locking and Serializable Snapshot Isolation.arrow_forwardIn the 2PL algorithm we considered, a transaction can't start until it has acquired all the locks it needs (we call this, Conservative 2PL). There is a different scheme possible, where a transaction does NOT need to wait for all its locks - it can start its transactions before all the locks have been acquired. What would be good about such a scheme, and, what would be bad? Do feel free to illustrate with a diagram.arrow_forward
- Consider a multi-granularity locking system, with lock modes S, X, IS, IX, and SIX as in lecture and database-level, file-level, page-level and record-level locking as shown in the following figure. Provide the sequence of lock requests required to perform the following transactions and write necessary complete Lock and Unlock operations in their correct order. T3 want to read all pages in F1 and modify about 10 pages, which can be identified only after reading F1.(MY ANSWER) Lock-SIX(DB); Lock-S(F1); Lock-X(P1); Lock-X(P1000); Unlock(P1000); Unlock(P1); Unlock(F1); Unlock(DB); is it corect? ………………………………………………………………………………………arrow_forwardSuppose the deferred modification technique is used in a database.a. Is the old value part of an update log record required any more?Why or why not? b. If old values are not stored in update log records, transaction undo isclearly not feasible. How would the redo phase of recovery have to bemodified as a result?c. Deferred modification can be implemented by keeping updated dataitems in local memory of transactions and reading data items that havenot been updated directly from the database buffer. Suggest how to efficientlyimplement a data item read, ensuring that a transaction sees itsown updates.d. What problem would arise with the above technique if transactions performa large number of updates?arrow_forwardWhat exactly is deadlock? What can be done to avoid it? When it occurs, how can it be resolved?arrow_forward
- What does it mean to have a stable database state? There is no assurance that the symbolic meaning of the transaction adequately captures the underlying real-world event as given by the database management system. What would the consequences of such a restriction be? Explain what you mean with a particular example. Is it true that the word "serializable transactions" means what it seems to mean?arrow_forwardWe 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) COMMITarrow_forwardProvide a high-level intuition for why log records for transactions on the undo-list must be processed in reverse order, whereas redo is performed in a forward direction. What can go wrong if the undo-list is processed in a forward direction or redo is performed in a backward order?arrow_forward
- Suppose you wish to create an audit trail of changes to the takes relation. Can the preceding implementation guarantee that updates made by a malicious database administrator (or someone who manages to get the administrator’s password) will be in the audit trail? Explain your answer.arrow_forwardProvide an explanation for the phenomena known as phantom limbs. Despite the usage of the two-phase locking scheme, why is it possible that this phenomena may result in improper concurrent execution?arrow_forwardTransaction management deals with the problems of always keeping the database in a consistent state even when concurrent accesses and failures occur. Isolation requires that each transaction sees a consistent database at all times and that an executing transaction cannot reveal its results to other concurrent transactions before its commitment. ANSWER If two concurrent transactions access a data item that is being updated by one of them, it is not possible to guarantee that the second will read the correct value. Dirty reads and nonrepeatable reads may occur when one transaction can see intermediate results of another transaction before it has been committed.. Given below are two concurrent transactions T1 and T2 whose balances of amount x (balx) were recorded at times t, between t₁ and tg. As shown in the table below: If these two transactions interfere with each other, fill in the table below by selecting from the drop down list the values of balance X (bal,) at specified times…arrow_forward
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