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 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?

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
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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 transaction sees its
own updates.
d. What problem would arise with the above technique if transactions perform
a large number of updates?
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