ITM 100 Lecture Notes - Lecture 16: Savings Account, Referential Integrity, Business Process

• School: Ryerson University
• Department: Information Technology Management
• Course: ITM 100
• Professor: Alec Cram

Document Summary

When inter-dependent transactions lock multiple records, the system can come to a halt. This is because each of these transactions has to wait for the others to complete before accessing the required fields, but no transaction on the list can complete because fields locked by other transactions. I enter an atm transaction to transfer ,000 from a joint checking account to a joint savings account. Before this transaction, the checking account and savings account balances are ,000 and ,000. At the same time, my wife uses ebanking to transfer ,000 from our joint savings account to our joint checking account. Now my transaction cannot read the savings account balance and my. In a database table, a non-key field may be a pk in another table, in which case, that non-key field is called a foreign key in the table where it is not a pk. For example, instructor id in a course table.