Suppose that you are a manufacturer of product ABC, which is composed of parts A, B, and C. Each time a new product ABC is created, it must be added to the product inventory, using the PROD_QOH in a table named PRODUCT. Also, each time the product is created, the parts inventory, using PART_QOH in a table named PART, must be reduced by one each of parts A, B, and C. The sample database contents are shown in the following tables.
| Table 10.1 |
| TABLE NAME: PRODUCT |
| PROD_CODE |
PROD_QOH |
| ABC |
1,205 |
|
|
|
|
| TABLE: PART |
| PART_CODE |
PART_QOH |
| A |
567 |
| B |
98 |
| C |
549 |
• Given the preceding information, answer Questions a through e.
1. How many database requests can you identify for an inventory update for both PRODUCT and PART?
2. Using SQL, write each database request you identified in Step a.
3. Write the complete transaction(s).
4. Write the transaction log, using Table 10.1 as your template.
5. Using the transaction log you created in Step d, trace its use in database recovery.
• Describe the three most common problems with concurrent transaction execution. Explain how concurrency control can be used to avoid those problems.
• What DBMS component is responsible for concurrency control? How is this feature used to resolve conflicts?
• Using a simple example, explain the use of binary and shared/exclusive locks in a DBMS.
• Suppose that your database system has failed. Describe the database recovery process and the use of deferred-write and write-through techniques.