Databases / Files

When you are thinking about the concepts in this lesson, things about the Visa Company's customer and purchaise files. These files are:

• huge
• have lots of changes every minute
• are important - if you loose something, it costs money
• lots of people need simultaneous access to updating the files
• you want security on your system. no unauthorized access.

File Manager A program that manages files by providing an interface between the user and the files. It does all of the above functions including: handles backups brings files back to a consistant state after the power goes out allows simultaneous access by multiple users. prevents unauthorized access

On-Line Processing

• in on-line processing the processing (adding records to the file, deleting records, searching and sorting, modifying records, accessing the records) occurs over a network
• the functions are normally split into two pieces. (a) client - on the user's computer. It makes requests and formats the results. (b) server - on the computer with the massive files. It goes into the file and handles the requests.
• with on-line processing there are signifigant security risks and signifigant problems with simultaneous access (two people might want to change the same thing at the same time).

Master File

• the company will record changes in a Master file.
• the time that these changes are processed is either: real-time processing or batch processing.