Oracle recommends that you use the following guidelines in reviewing your ODA_BASE resource allocation, and in carrying out resizing.
Increase the number of CPU cores assigned to the ODA_BASE domain on Oracle Database Appliance Virtualized Platform if you need more computing power or memory for your installed Oracle databases. Alternatively, decrease the CPU cores if you need more CPUs assigned to your virtual machine domains. You must increase or decrease the assigned CPU core count on each node by two or multiples of two.
Oracle recommends that you use templates to size the databases that you deploy in ODA_BASE, following the guidelines in Appendix A of Oracle Database Appliance Getting Started Guide. Sum the number of CPUs that these databases require, using the tables in that appendix, and divide the value by two to determine the number of CPU cores that you require for ODA_BASE.
The ODA_BASE domain shuts down during the resizing process. For this reason, plan to change your ODA_BASE core count either when there is no critical activity running on your Oracle databases, or when you schedule a planned maintenance window.