Change sets can help you preview the impacts of changes to stacks before you implement the changes on stacks. You can create multiple change sets for a stack in Resource Orchestration Service (ROS) to meet your business requirements.
Change set overview
A change set contains changes that are implemented to manage and execute a template. You can use a change set to manage and update resources. Change sets can help you check whether resources can be updated and whether stacks are affected. Before you execute a change set on a stack, you can preview how proposed changes impact the stack. ROS makes the changes to your stack only after you successfully execute the change set. For more information about how changes are made to a stack by using a change set, see Data structures.
Scenarios
Use a change set to create a stack
If you want to manage a large number of cloud resources and preview the creation effect of the resources before a stack that contains the resources is created, you can create the stack by using a change set. You must use this feature together with the resource import feature. For more information, see Import an existing resource to create a stack. You can use the resource import feature to import cloud resources to create a stack. Then, you can use a change set to preview the creation effect of the resources before the stack takes effect. A stack can manage cloud resources as expected only after you successfully execute the change set on the stack. Before you execute a change set, you can check and modify the stack template to meet your business requirements.
For more information, see Use a change set to create a stack.
Use a change set to update a stack
If you want to preview the impacts of changes to a stack before you update the stack resources, you can update the stack by using a change set. For example, you can preview whether key resources are deleted or replaced by a stack update. You can create a change set to update the stack. The change set helps you preview impacts of the update operation on the stack before the stack update takes effect. The stack update takes effect only after you successfully execute the change set on the stack. Before you execute a change set, you can check and modify the template of the stack that you want to update to meet your business requirements.
For more information, see Use a change set to update a stack.
Limits
You can use change sets to update only stacks that are in specific states. For more information, see Use a change set to update a stack.
You can associate up to 20 change sets with a stack.
Change sets reflect only the changes to stacks. Change sets do not reflect whether stacks are successfully updated.
A change set does not check if you exceed an account limit, if you update resources that cannot be updated, or if you have insufficient permissions to modify resources, all of which can cause a stack update to fail. If a stack update fails, ROS attempts to roll back your resources to their original status.
Feature comparison
Compared with the operation to directly update a stack, the following differences exist in the operation to update a stack by using a change set. For more information, see Use a change set to update a stack and Update a stack.
A stack update takes effect only after you successfully execute the change set on the stack.
A change set allows you to preview the impacts of changes to a stack before the stack takes effect.
A change set allows you to check and modify the template of a stack before the stack takes effect.
References
You can view the impacts of a change set on a stack and check the stack template. For more information, see View a change set and Data structures.
After you execute a change set on a stack, ROS automatically deletes other change sets that are associated with the stack. For more information, see Execute a change set.
If a change set cannot meet your business requirements on a stack update, you can delete the change set. For more information, see Delete a change set.