Textbook Problem

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Assuming that pessimistic locking is being used with the two-phase locking protocol, create a chronological list of the locking, unlocking, and data manipulation activities that would occur during the complete processing of the transaction described in Problem 6a.

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.

Explanation of Solution

Chronological list:

The following chronological list demonstrate locking, unlocking, and data manipulation activities of transaction described in “Problem 6a” using pessimistic locking method with the two-phase locking protocol.

Time	Action
1	Lock INVOICE
2	Lock LINE
3	Lock PRODUCT
4	Lock CUSTOMER
5	Insert row 10983 into INVOICE
6	Insert tow 10983, 1 into LINE
7	Update PRODUCT 11QER/31, P_QTYOH from 47 to 46
8	Update CUSTOMER 10010, CUS_BALANCE from 345...