Large, mission critical applications built on Oracle Database 11g Release 1 and earlier
versions are often unavailable for tens of hours while the application’s database objects
are patched or upgraded. Oracle Database 11g Release 2 introduces edition-based
redefinition, a revolutionary new capability that allows online application upgrade with
uninterrupted availability of the application. When the installation of the upgrade is
complete, the pre-upgrade application and the post-upgrade application can be used at
the same time. Therefore an existing session can continue to use the pre-upgrade
application until its user decides to end it; and all new sessions can use the post-upgrade
application. As soon as no sessions are any longer using the pre-upgrade application, it
can be retired. In other words, the application as a whole enjoys hot rollover from the
pre-upgrade version to the post-upgrade version.
This whitepaper explains how edition-based redefinition works, and how to write online
application upgrade scripts using this capability, at the level of detail needed by engineers
who will write such scripts.
