The Oracle Omotion
instance migration utility
Omotion is an online migration utility (new in 11gR2) that is used with
RAC One Node to facilitate super fast
instance relocation is cases of server failure. This is part of Oracle
Corporations' acknowledgement of the
server consolidation movement and the 2nd age of mainframe computing.
While details from Oracle are sketchy, it's a safe bet that Omotion performs
instance relocation is a fashion similar to it's predecessors,
Savantis Systems with their
invention, an offshoot of the Database Area Network (DAN)
Savantis Systems uses a high-speed database switch (dbSwitch™) which is
placed between the application layer and the database layer. This switch
enables Oracle databases to be transparently relocated onto new servers
without the need to modify applications connections to the database.
In a similar fashion, Oracle Omotion might use a SAN, whereby a new server
(preloaded with an instance init.ora file), should acquire the database
files from the SAN, mount them to the new server, and quickly re-start the
The Database Area Network (DAN) architecture.
See here for details on
how Oracle instance relocation works using DAN and SAN technology.
In the olden days, we did instance relocation with a SAN environment, using
the following steps:
1. The Oracle instance or the server crashes.
dead connection probe (DCD) detects the outage and we un-mount the SAN data
file systems from the source server (if it's awake).
3. We then mount the database files onto the failover
server using SAN.
4. We re-start the instance on the new server,
using a pre-loaded init.ora file.
5 We use a failover routing
mechanism like transparent application failover (TAF) to redirect
transactions accessing the database (VIP) to the new server.
A typical time for an Oracle instance relocation is less than 20 seconds,
not true continuous availability, but certainly better than a catastrophic
Oracle Instance relocation make sense!
An instance relocation scheme makes sense because it uses far less resources
than Data Guard (which requires a standby server) and Streams failover.
With instance relocation, a single standby server might serve for hundreds
Dynamic instance relocation can make Oracle
databases behave like "black boxes." This means that the OS architecture is
not important because the database is independent of the OS. For example,
Oracle Omotion likely allows relocation to any OS with the same Endian
format, including AIX, Linux, Solaris, or HP/UX.
As this Omotion technology matures, it's likely
that predictive analytics might be used to predict when the database will
experience stress and relocate it to a larger server, just in time to
accommodate the increased processing need.