Edition-based redefinition (EBR), enables online application upgrade with uninterrupted availability of the application. When the installation of an upgrade is complete, the pre-upgrade application and the post-upgrade application are able to 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. When there are no longer any sessions using the pre-upgrade application, it can be retired. When used in this manner, EBR enables hot rollover from the pre-upgrade version to the post-upgrade version, with zero downtime.
EBR is an included feature of Oracle Database 11g Release 2 that enables online application upgrades in the following manner:
Code changes are installed in the privacy of a new edition.
Data changes are made safely by writing only to new columns or new tables not seen by the old edition. An editioning view exposes a different projection of a table into each edition to allow each to see just its own columns..
A crossedition trigger propagates data changes made by the old edition into the new edition’s columns, or (in hot-rollover) vice-versa..