Database System Concepts
Database System Concepts
7th Edition
ISBN: 9780078022159
Author: Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher: McGraw-Hill Education
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Chapter 25, Problem 2PE

Explanation of Solution

a)

Sequence counter in two phase manner:

  • The sequence counter remains locked in two phase in exclusive mode till it acquires the lock from other transaction
  • There might be data conflict during the transaction with...

Explanation of Solution

b)

i. Improving the concurrency using counters:

  • When the transaction abort it does not create any problems and increment operation can be performed easily on the counter.
  • It cannot retain its original position during an abort. But it remains as it stands.
  • So, there might be gaps in the sequence number as the counter cannot be restored to its previous value.
  • These values are assigned to its aborted transactions.

ii. Gaps in sequence numbers:

  • For example assume the counter value which cannot restore to its previous value during transactions...

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