Database Reference
In-Depth Information
Further Reading
Xen-based para-virtualization is a very fascinating topic, which is far too encompassing to explain it in its entirety
here. Since Oracle VM Server for x86 is based, to a large extent, on the free hypervisor, it makes a lot of sense to
understand Xen before diving into Oracle's implementation details. One of the best resources, when it comes to Xen,
is the home of Xen:
http://www.xen.org
. The website has a very useful wiki as well, accessible as
wiki.xen.org
.
Additional useful resources include:
•
Oracle® VM Release Notes for 3.1.1(E27307-05)
•
Oracle® VM Getting Started Guide for Release 3.1.1 (E27312-03)
•
Xen 4.1.2 release notes:
•
Xen manual pages:
Final Thoughts on Virtualization
The previous sections have given you a high-level overview of different approaches to virtualization. There is most
likely a virtualization initiative underway in your company, but most users thus far have only virtualized development
and UAT/pre-production environments. The most critical, production and the corresponding disaster recovery
environments have most often remained untouched.
During the research for this chapter, a large international company announced that it has completely virtualized
their SAP environment, demonstrating that virtualization can work even for production environments. There are
some common pitfalls, however. Some users have gone too far with their virtualization strategy. There is a reported
case in which one Unix domain containing one Oracle home plus nine databases has been virtualized in nine
different virtual machines on x86, each with its own operating system, an own Oracle home and only one database.
Although the approach has certainly helped increase isolation between the environments, it has also increased the
management overhead. In such a scenario, it is even more important to either not create as many virtual machines or,
if that cannot be avoided, have a suitable management strategy for mass-patching operating system and databases.
Thankfully, Oracle database 12c and the multi-tenancy option gives administrators similar levels of isolation at
reduced overhead of having to maintain too many copies of the operating system.
If done right, virtualization offers tremendous potential and can challenge traditional clustered solutions for uptime
and availability. The established companies in the market have very mature and elaborate management frameworks,
allowing the administrator to control his environment. It can help contain what the industry refers to as “server sprawl.”
Recently, vendors are also pushing into the new
yourProductHere
as a service market. Times are interesting!
High Availability Example
You read in the introduction that there are additional ways to protect a single instance Oracle database from failure.
We have just thoroughly covered the virtualization aspect, mainly because virtualization is such a big driver of innovation
in the industry. In addition to virtualization, you have the option to use more than one physical server to protect the
instance from hardware failures. The following section provides more information on how to achieve this goal.
You might want to consider that strict high availability requirements often come down in a way to be compatible
with an active/passive cluster. However, if your requirements are such that even the short interruption of service is
intolerable then you need to have a look at the Real Application Cluster option. Similar to the previous section, this
section presents an example for an active/passive cluster based on Oracle Clusterware. It is assumed that you have
some background knowledge about clustering.
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