How Much Load Capacity Should You Provision for Your Instance?

Depending on the load your applications are placing on your server, you might want to resize your instance to ease the server load and improve the response time. You can use the instance metrics to help you calculate how much of the server's capacity your applications are using.

Oracle uses Oracle Compute Units (OCPU) to measure the compute capacity of your instance, and for billing puposes. Each OCPU is equivalent to one virtual machine (VM). When provisioning and sizing a Visual Builder instance, each VM is represented by a node. By default, your Visual Builder instance is provisioned with two VMs, however, you are only billed for one node (one OCPU). If you increase the compute capacity of your instance by adding nodes, you will be billed for an additional OCPU for each node you add. You can see the number of nodes in the instance on the instance's details page.

The number of nodes to provision will depend on the architecture of your applications, as well as the load placed on the server by users. When thinking about how many VMs you need, and when to increase the size of your instance, it's helpful to think about how many transactions per second the server needs to handle. For example, if you have 100 users in an hour, each making 60 REST calls during that hour, then the server will need to handle 6000 transactions per hour. This translates to roughly 1.7 transactions per second (6000 transactions/3600 seconds per hour).

The type of transactions will affect the load placed on the server. The default Visual Builder configuration of two VMs can handle a load of roughly 4.5 read transactions per second, and 1.3 write transactions per second. This means a VB instance can easily serve 16,000 read transactions and 5000 write requests per hour.

The design of your applications will also affect the load placed on the server. An application that is using the business object layer in Visual Builder, and the built-in database, places a heavier load on a server than an application that uses external REST services, with the VB server acting as a middle-tier used to access external data.

How can I view the metrics for my instance?

To help you calculate how much of your instance's capacity you are using, and if you might need to add capacity, you can get a good idea by running your application and using the charts in the Monitoring tab to view your instance's current OCPU consumption, database usage, and the number of users. See View Instance Metrics.

For each chart, you can choose the function used for rendering the data, and in most cases you will want to use either the mean or the max function. For example, when view the data on the number of users and database usage in a given period, you would typically want to use the max function to see the highest values; for the OCPU consumption, you would want to use the mean function. The OCPU consumption chart displays separate lines for each of your instance's VMs. By default, the chart will have two lines, one for each of the two VMs provisioned by default with Visual Builder.

If you see that you are using most of the OCPU capacity, you might want to consider adding a node to scale up the server capacity.

How do I scale up server capacity?

By default, your instance is provisioned with two VMs. If you need to scale up the size of your instance, you can add VMs by adding nodes. Adding one node adds one VM, and one OCPU to the billing. See Scale a Visual Builder Instance.