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Oracle PL/SQL Programming, 5th Edition by Bill Pribyl, Steven Feuerstein

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Introduction to Edition-Based Redefinition (Oracle Database 11g Release 2)

One of the most significant enhancements in Oracle Database 11g Release 2 is surely edition-based redefinition, a new element of Oracle’s high availability solution. This feature makes it possible to upgrade the database component of an application while it is being used; that is, Oracle now supports “hot patching” of PL/SQL-based applications. Edition-based redefinition will make it possible to minimize or completely eliminate downtime for maintenance.

With edition-based redefinition, when you need to upgrade an application while it is in use, you make a copy of any affected database objects in the application and redefine the copied objects in isolation from the running application. Any changes you make are not visible to nor have any effect on users. Users can continue to run the application as it existed before your changes (to this new edition). When you are certain that all changes are correct, you then make the upgraded application available to all users.

As you can imagine, adding this feature has had a sweeping impact on the Oracle database. For example, if you want to see a list of all the objects you have defined, instead of writing a query against ALL_OBJECTS, you can now query the contents of ALL_OBJECTS_AE (“All Editions”). The unique specifier for an object is now OWNER, OBJECT_NAME, and EDITION_NAME (assuming, in any case, that the owner is editions-enabled) This one aspect is just the tip of ...

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