The snapshot isolation protocol uses a validation step which, before performinga write of a data item by transaction T, checks if a transaction concurrentwith T has already written the data item.a. A straightforward implementation uses a start timestamp and a committimestamp for each transaction, in addition to an update set, that, is theset of data items updated by the transaction. Explain how to performvalidation for the first-committer-wins scheme by using the transactiontimestamps along with the update sets. You may assume that validationand other commit processing steps are executed serially, that is, for onetransaction at a time,b. Explain how the validation step can be implemented as part of commitprocessing for the first-committer-wins scheme, using a modification ofthe above scheme, where instead of using update sets, each data itemhas a write timestamp associated with it. Again, you may assume thatvalidation and other commit processing steps are executed serially.c. The first-updater-wins scheme can be implemented using timestamps as described above, except that validation is done immediately after acquiringan exclusive lock, instead of being done at commit time.i. Explain how to assign write timestamps to data items to implementthe first-updater-wins scheme.ii. Show that as a result of locking, if the validation is repeated at committime the result would not change.iii. Explain why there is no need to performvalidation and other commitprocessing steps serially in this case.

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

See similar textbooks

Related questions

Concept explainers

Question

The snapshot isolation protocol uses a validation step which, before performing
a write of a data item by transaction T, checks if a transaction concurrent
with T has already written the data item.
a. A straightforward implementation uses a start timestamp and a commit
timestamp for each transaction, in addition to an update set, that, is the
set of data items updated by the transaction. Explain how to perform
validation for the first-committer-wins scheme by using the transaction
timestamps along with the update sets. You may assume that validation
and other commit processing steps are executed serially, that is, for one
transaction at a time,
b. Explain how the validation step can be implemented as part of commit
processing for the first-committer-wins scheme, using a modification of
the above scheme, where instead of using update sets, each data item
has a write timestamp associated with it. Again, you may assume that
validation and other commit processing steps are executed serially.
c. The first-updater-wins scheme can be implemented using timestamps as described above, except that validation is done immediately after acquiring
an exclusive lock, instead of being done at commit time.
i. Explain how to assign write timestamps to data items to implement
the first-updater-wins scheme.
ii. Show that as a result of locking, if the validation is repeated at commit
time the result would not change.
iii. Explain why there is no need to performvalidation and other commit
processing steps serially in this case.

Expert Solution

Trending now

This is a popular solution!

Step by step

Solved in 2 steps

SEE SOLUTION Check out a sample Q&A here

Knowledge Booster

Learn more about

Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, computer-science and related others by exploring similar questions and additional content below.

Similar questions