CS338 Lecture Notes - Lecture 15: Database Model, Savings Account, Online Transaction Processing

• School: University of Waterloo
• Department: Computer Science
• Course: CS338
• Professor: Angela Bonifati

Document Summary

Each execution of a program is a distinct transaction with different parameters. Bank transfer program parameters: savings account number, chequing account number, transfer amount. Online transaction processing (oltp) systems: large multi-user database systems supporting thousands of concurrent transactions (user processes) per minute. Database is a shared resource accessed by many users and processes concurrently. Not managing this concurrent access will cause problems: problems due to concurrency, problems due to failures. Simple database model: database: collection of named data items, granularity: size of each data item immaterial, field, record or a disk block, tp concepts are independent of granularity. Basic operations on an item x: read_item(x): reads a database item x into a program variable, write_item(x): writes the value of program variable x into the database item named x. Processor registers, processor cache, ram, flash/ usb memory, hard drives, tape backup. Basic unit of data transfer from the disk to the computer main memory is one disk block or page.