As the usage of application grows within the organization, adding additional server nodes is the best way to achieve the required performance and scalability.
If the application usage model exhibits seasonality, or periodic variations (for example, the average load on the system quadruples during month-end closing, or a plant may close for a week every quarter for maintenance), then consider adding, or removing, application server nodes in order to manage seasonality usage spikes.
To mitigate the risk of degraded performance and undesired downtime, it is crucial to understand the business cycles of your organization and to plan for the required level of performance, availability, and scalability.
There are two ways to add application server nodes in a deployment:
- Vertical clustering
- Horizontal clustering
Vertical clustering
In cases where you observe that the application transaction response times are degraded due to increased usage, if the hardware resources of the server (Memory and CPU) have enough head room, then you can implement vertical clustering by adding two, or more, server nodes of the application on the same physical server.
The following figure shows vertical clustering.
Horizontal clustering
In cases where you observe that the application transaction response times are degraded due to increased usage, if the hardware resources of the server (Memory and CPU) do not have enough head room, you can implement horizontal clustering by adding another server and installing a Unifier instance on the added server.
The horizontal clustering is shown in the Horizontal Scaling section of this guide.
For high availability scenarios, Oracle recommends horizontal clustering in production systems. A mix of horizontal and vertical clustering is recommended for large deployments.
Note: While creating application clusters, the administrator must monitor the database server resource utilization. If the database performance worsens, then the administrator must tune the database or upgrade the hardware.