"The term rolling upgrade refers to upgrading
different databases or different instances of
the same database (in a Real Application
Clusters environment) one at a time, without
stopping the database.
The advantage of a RAC rolling upgrade is that
it enables at least some instances of the RAC
installation to be available during the
scheduled outage required for patch upgrades.
Only the RAC instance that is currently being
patched needs to be brought down. The other
instances can continue to remain available. This
means that the impact on the application
downtime required for such scheduled outages is
further minimized. Oracle's opatch utility
enables the user to apply the patch successively
to the different instances of the RAC
installation.
Rolling upgrade is available only for patches
that have been certified by Oracle to be
eligible for rolling upgrades. Typically,
patches that can be installed in a rolling
upgrade include:
- Patches that do not affect the contents
of the database such as the data dictionary
- Patches not related to RAC internode
communication
- Patches related to client-side tools
such as SQL*PLUS, Oracle utilities,
development libraries, and Oracle Net
- Patches that do not change shared
database resources such as datafile headers,
control files, and common header definitions
of kernel modules
- Rolling upgrade of patches is currently
available for one-off patches only. It is
not available for patch sets.
Rolling patch upgrades are not available for
deployments where the Oracle Database software
is shared across the different nodes. This is
the case where the Oracle home is on Cluster
File System (CFS) or on shared volumes provided
by file servers or NFS-mounted drives. The
feature is only available where each node has
its own copy of the Oracle Database software."
