Unit 19.5. Read-Consistent Updates

Data Consistency

When generating Web pages with PL/SQL you cannot use the traditional database locking schemes because HTTP is a stateless protocol. Think about this example. You go to update the information for the instructor, Nina Schorin. You get to the Web page to view her personal information. But then you run out of the room and come back. In this time, another user on another computer updates the zipcode for Nina Schorin. Now you go and try to update her street address, but you just had the old zipcode in your form. The question is: Which version of the zipcode should be saved?

To handle this situation, Oracle provides a PL/SQL package called OWA_OPT_ LOCK that lets you utilize “optimistic locking.” ...

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