Oracle Database High Availability
Edition-Based Redefinition (EBR)
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 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. When there are no longer any sessions using the pre-upgrade application, it can be retired. In this way, EBR allows hot rollover from from the pre-upgrade version to the post-upgrade version, with zero downtime.
EBR 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.
- Crossedition triggers propagate data changes made by the old edition into the new edition’s columns, or (in hot-rollover) vice-versa.
EBR is available for use in all editions of Oracle Database without the need to license it.