Exadata and Capacity on Demand (CoD)

As most of us knew that the Exadata Database Machine comes in different sizes with different resource capacity. Not sure how many of you aware that Capacity on Demand (CoD) option can enable customers to start with limited active cores processors and increase them dynamically on demand. If CoD option is not enabled during the initial EDM configuration, then, all active cores are enabled by default and can't be reduced any further.

With X4-2 or higher, number of active cores can be reduced during the installation and can be increased based on the demand.  For X4-2, cores are increased in two (2) core increment, where as X4-8 increased in eight (8) core factor, see the table below.

Below example demonstrates the procedure to increase the active core processors:

Using DBMCLI utility:

DBMCLI> LIST DBSERVER attributes coreCount

DBMCLI> ALTER DBSERVER pendingCoreCount = new_core_count

DBMCLI> LIST DBSERVER attributes coreCount

Note: Once active cores are enabled (increased), there is no procedure to reduce them again.

Restart the database servers after increasing the core count.

Below table depicts the capacity-on-demand core configuration for various EDM types and releases:

Updates (10-Oct-2018):
Came across of the below blog post where the author described the procedure how to reduce the core count on Exadata.
I haven't tested though, and also not sure whether this is an Oracle approved approach to reduce the core factor on Exadata. However, its good to know the procedure.

https://grepora.com/2018/10/08/reduce-exadata-core-count/