| RAC stands for Real Application Clusters. Oracle has a host of tools that facilitate scalability. Oracle RAC is commonly used for scalable Oracle solutions. Oracle Real Application Cluster (RAC) allows multiple nodes in a clustered environment to mount and open a single database that resides on shared disk storage. Should a single system (node) fail, the database service will still be available on the remaining nodes. |
| RAC has the ability to quickly add an entire server to a cluster increasing the horsepower without effecting end-user response time. RAC is a recommended solution when you have saturated a single server. |
| Grid Computing |
| The idea of Grid computing arose from the need to solve highly-parallel computational problems that were beyond the processing capability of any single computer. Oracle Grid computing technology represents a significant rethinking of the traditional role of software infrastructure in areas such as system performance, clustering and storage. |
| What is a Scale up approach? |
| In this approach, server resources (CPU, RAM, Disk) can be added into a single, monolithic server, which can have slots for up to 64 CPU’s and over 256 Gigabytes of RAM. Eg: HP Superdome (64 CPU), the Unisys ES-7000 Series (32 Processors), the Sun Microsystems SunFire and the IBM X and Regatta class servers. |
| What is Scale out approach? |
| The "scale out" approach is designed for super large Oracle databases that support many thousands of concurrent users. Unless the system has a need to support more than 10,000 transactions per second, it is likely that the system will benefit more from a scale up approach. |
| In the real world, managing vary large number of transactions, a scale up scale out approach may be used. Organizations start with a large vertical architecture server, adding resources as-needed. If continuous availability is also required, they may have a mirrored server using long-distance RAC or Oracle Streams. |
| Amazon is an excellent example of a scale out Oracle scale out approach. Amazon announced plans to move their 14 trillion byte Oracle database to Oracle RAC on Linux and Amazon uses load-balanced Linux Web servers to horizontally scale its Web presence to millions of connected users. |
There are two architectural models – commonly referred as SAAS Maturity models- that describe the transition of a service to what is called Multi-tenant efficient, highly scalable application. The SAAS Maturity model described by Microsoft has four distinct stages and is illustrated below. Another similar well-known model for SaaS-maturity is known as Forrester-model but adds another stage known as "Dynamic Business Apps-as-a-service". The three key Attributes of a SAAS Architecture: Configurability: Metadata used to configure the way the application behaves for customers Multi-tenant Efficiency : Maximizing the sharing of resources across tenants Scalability: Maximizing concurrency, resource efficiency SAAS Simple Maturity Model (Microsoft, 2006) SaaS Maturity Model (Forres
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