Database Systems: Design Implementation & Management
11th Edition
ISBN: 9781305850378
Author: Coronel
Publisher: Cengage
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Chapter 10, Problem 8P
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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Chapter 10 Solutions
Database Systems: Design Implementation & Management
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- What does it mean for a database to have a stable state? There is no guarantee that the transaction's symbolic meaning accurately represents the underlying real-world event as provided by the database management system. What would be the effects of this restriction? Give a specific illustration of what you mean. Does the term "serializable transactions" really imply what it seems to mean?arrow_forwardWhat is a stable database state, and how is it achieved?The DBMS gives no guarantee that the symbolic notion of the transaction appropriately matches the underlying real-world event.What are the possible consequences of the restriction? Please provide an example. What exactly is meant by "serializable transactions"?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_forward
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- What does it mean for a database to be in a stable state? The database management system does not ensure that the transaction's symbolic meaning appropriately reflects the underlying real-world event. What would be the repercussions of such a ban? Using a concrete illustration, clarify your meaning. Does the word "serializable transactions" imply what it seems to mean?arrow_forwardCan you define a database's stable state? The symbolic significance of the transaction may differ from its actual occurrence in the database management system. To what extent would a prohibition be felt? Give an instance to illustrate your point. Is there really anything to "serializable transactions"?arrow_forwardDifferentiate strict two phase locking protocol and rigorous two phase locking protocol.arrow_forward
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