When the emergency is over (or the CBU test is complete), the system must be returned to its original configuration. The CBU features can be deactivated at any time before the expiration date. Failure to deactivate the CBU feature before the expiration date can cause the system to downgrade resources gracefully to the original configuration. The system does not deactivate dedicated engines, or the last of in-use shared engines. 

Planning:  CBU for processors provides a concurrent upgrade. This upgrade can result in more enabled processors, changed capacity settings that are available to a system configuration, or both. You can activate a subset of the CBU features that are ordered for the system. Therefore, more planning and tasks are required for nondisruptive logical upgrades. For more information, see “Guidelines to avoid disruptive upgrades” on page 360. 

For more information, see the IBM Z Capacity on Demand User’s Guide , SC28-6846. 

## 8.7.2 CBU activation and deactivation 

The activation and deactivation of the CBU function is your responsibility and does not require the onsite presence of IBM SSRs. The CBU function is activated or deactivated concurrently from the HMC by using the API. On the SE, CBU is activated by using the Perform Model Conversion task or through the API. The API enables task automation. 

## CBU activation 

CBU is activated from the SE by using the HMC and SSO to the SE, by using the Perform Model Conversion task, or through automation by using the API on the SE or the HMC. 

During a real disaster, use the Activate CBU option to activate the 90-day period. 

## Image upgrades 

After CBU activation, the z14 server can have more capacity, more active PUs, or both. The extra resources go into the resource pools and are available to the LPARs. If the LPARs must increase their share of the resources, the LPAR weight can be changed or the number of logical processors can be concurrently increased by configuring reserved processors online. 

The operating system must concurrently configure more processors online. If necessary, more LPARs can be created to use the newly added capacity. 

## CBU deactivation 

To deactivate the CBU, the extra resources must be released from the LPARs by the operating systems. In some cases, this process is a matter of varying the resources offline. In other cases, it can mean shutting down operating systems or deactivating LPARs. After the resources are released, the same facility on the HMC/SE is used to turn off CBU. To deactivate CBU, select the Undo temporary upgrade  option from the Perform Model Conversion task on the SE. 

## CBU testing 

Test CBUs are provided as part of the CBU contract. CBU is activated from the SE by using the Perform Model Conversion task. Select the test option to start a 10-day test period. A standard contract allows one test per CBU year. However, you can order more tests in increments of one up to a maximum of 15 for each CBU order. 

