Database Reference
In-Depth Information
Chapter 1
Overview of Oracle RAC
by Kai Yu
In today's business world, with the growing importance of the Internet, more and more applications need to be
available online all the time. One obvious example is the online store application. Many companies want to keep their
online stores open 24x7 on 365 days so that customers from everywhere, in different time zones, can come at any time
to browse products and place orders.
High Availability (HA) may also be critical for non-customer-facing applications. It is very common for IT
departments to have complex distributed applications that connect to multiple data sources, such as those that extract
and summarize sales data from online store applications to reporting systems. A common characteristic of these
applications is that any unexpected downtime could mean a huge loss of business revenue and customers. The total
loss is sometimes very hard to quantify with a dollar amount. As the key components of these applications, Oracle
databases are often key components of a whole storefront ecosystem, so their availability can impact the availability of
the entire ecosystem.
The second area is the scalability of applications. As the business grows, transaction volumes can double or
triple as compared to what was scoped for the initial capacity. Moreover, for short times, business volumes can be
very dynamic; for example, sales volumes for the holiday season can be significantly higher. An Oracle Database
should be scalable and flexible enough to easily adapt to business dynamics and able to expand for high workloads
and shrink when demand is reduced. Historically, the old Big Iron Unix servers that used to dominate the database
server market lacked the flexibility to adapt to these changes. In the last ten years, the industry standard has shifted to
x86-64 architecture running on Linux to meet the scalability and flexibility needs of growing applications. Oracle Real
Application Clusters (RAC) running on Linux on commodity X86-64 servers is a widely adapted industry-standard
solution to achieve high availability and scalability.
This chapter introduces the Oracle RAC technology and discusses how to achieve the high availability and
scalability of the Oracle database with Oracle RAC. The following topics will be covered in this chapter:
•
Database High Availability and Scalability
•
Oracle Real Application Clusters (RAC)
•
Achieving the Benefits of Oracle RAC
•
Considerations for Deploying Oracle RAC
High Availability and Scalability
This section discusses the database availability and scalability requirements and their various related factors.
