Database Systems: Design, Implementation, & Management
11th Edition
ISBN: 9781285196145
Author: Steven, Steven Morris, Carlos Coronel, Carlos, Coronel, Carlos; Morris, Carlos Coronel and Steven Morris, Carlos Coronel; Steven Morris, Steven Morris; Carlos Coronel
Publisher: Cengage Learning
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Chapter 10, Problem 9P
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.
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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?
………………………………………………………………………………………
Transaction 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…
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"?
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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- Suppose 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. Is clearly not feasible. How would the redo-phase of recovery have to be modified as a result? C. Deferred modification can be implemented by keeping updated data items in local memory of transactions, and reading data items that have not been updated directly from the database buffer. Suggest how to efficiently implement a data item read, ensuring that a trans action sees its own updates.arrow_forwardWhen the application of an optimistic approach to concurrency control is implemented, it is frequently observed that transactions experience prolonged durations for completion. Explain?arrow_forwardIn a database transaction, the two main operations are READ and WRITE operations. So, there is a need to manage these two operations in the concurrent execution of the transactions as if these operations are not performed in an interleaved manner, and the data may become inconsistent. Consider the following scheduled transactions T1, T2, T3, and T4. T1 T2 T3 T4 Reads(X) Writes(X) Reads(Y) Writes(Y) Commit Reads(X) Time Reads(X) Writes(X) Reads(Y) Rollback Writes(Y) Writes(X) Commit • Identify all pair of transactions based on the occurred problem between two transactions (specify pairs, e.g., T1 => T2; T3=> T2; T3 =>T4; etc.). • Specify the name of a problem for each detected pair of transactions. • Justify the occurred problem for each pair of transactions.arrow_forward
- An answer to this question: What does it mean to have a stable database state? There is no guarantee that the transaction's symbolic meaning accurately represents the underlying real-world event provided by the database management system. What would be the ramifications of such a prohibition? Using a specific example, explain what you mean. Does the term "serializable transactions" really mean what it appears to?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_forwardExplain the concept of serializability in the context of concurrency control. How is it different from other forms of consistency, such as linearizability or strict two-phase locking?arrow_forward
- Consider a database system that includes an atomic increment operation, in addition to the read and write operations. Let V be the value of data item X.The operation increment(X) by C sets the value of X to V + C in an atomic step. The value of X is not available to the transaction unless the latter executes a read(X).Assume that increment operations lock the item in increment mode using the compatibility matrix in Figure 18.25.a. Show that, if all transactions lock the data that they access in the corresponding mode, then two-phase locking ensures serializability.b. Show that the inclusion of increment mode locks allows for increasedconcurrency.arrow_forwardConsider 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 ( picture bellow ) I want to get "T3 want to read all pages in F1 and modify about 10 pages, which can be identifiedonly after reading F1."arrow_forwardQuestion 1: True or False Question Answer We need transactions management for system effectiveness. In an E/R diagram, the relations cannot have their own keys. In a database system, we use write-ahead logging to achieve concurrency. We should avoid interleaving transactions. A schedule with Write-Write conflicts cannot be converted to a serial schedule. In strict 2PL, the program cannot access to the data when there is a lock on it. We prefer RAM than Disk since it is durable. The external merge sort algorithm can be complete with as little as two buffer pages.arrow_forward
- All transactions have four properties: Atomicity, Consistency, Isolation, and Durability. These four properties are also known as the ACID test of transactions. In addition, multiple transactions must conform to the property of serializability. Concurrency controlling techniques ensure that multiple transactions are executed simultaneously while maintaining the ACID properties of the transactions and serializability in the schedules. Explain the following statement: a transaction is a logical unit of work.What are some disadvantages of time-stamping methods for concurrency control?Why might it take a long time to complete transactions when an optimistic approach to concurrency control is used?arrow_forwardThe implementation of an optimistic concurrency control strategy frequently results in the postponement of transactions. Explain?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_forward
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