Modern information systems run transactions in parallel. Running hundreds or even thousands of transactions at the same time is commonplace for information systems today. Transactions running at the same run into many issues, including lost updates, uncommitted dependencies, inconsistent analysis, and others. To eliminate and manage these issues, modern relational databases use a scheduler which controls the schedule and timing of transaction execution, in addition to other mechanisms. You have a chance to demonstrate an understanding of concurrency control in this section. In this section, the questions refer to the following data table, as well as the following transactions and steps. Data Table

1

2

3

4

5

Transaction 1

Read the value from row 4.

Multiply that value times 3.

Write the result to row 3.

Write the literal value "8" to row 2.

Write the literal value "20" to row 5. Commit. ]

Transaction 2 Read the value from row 2.

Write that value to row 4.

Write the literal value "15" to row 3.

Commit.

Issues with No Concurrency Control - Imagine the transactions for this section are presented to a modern relational database at the same time, and the database does not have concurrency control mechanisms in place. Show a step-by-step schedule that results in a lost update, inconsistent analysis, or uncommitted dependency. Also, list out the contents of the table after the transactions complete using the schedule. You only need to show a schedule for one of the issues, not all three. You are not creating this table in SQL, so it is fine to show the table in Excel or Word. 2.

Issues with Locking and Multiversioning - Imagine the database has both locking and multi-versioning in place for concurrency control.

a. Starting with the same schedule in the prior step, show step-by-step how the use of locking and multi-versioning modifies the schedule, and also list out the contents of the table after the transactions complete using the new schedule.

b. Could a schedule of these transactions result in a deadlock? If not, explain why. If so, show a step-by-step schedule that results in a deadlock.