Change a project issue type schema

[j]

Hello,

Will it cause problems to an existing project if I change the issue type schema from
 

Default Issue Type Schema

to 

Agile Scrum Issue Type Schema

I am unsure if there were ever issue types that were created that will not correctly map to the new schema.  I want to clean up and standardize the issue types that can be created.

Thanks in advance for your help.

[Nic Brough -Adaptavist-]

It might, but only problems with your data.  Possibly.

When you go into the scheme selection scheme, you will be shown the issue types that are in the schemes, which can be quite helpful.  

There are four possible changes you might make here, and only one of them has a significant data impact

1. Source and target scheme are the same (you might do this just to de-duplicate schemes)
2. Source scheme is a sub-set of the target - all the issue types in the old scheme are present in the new one
3. The source scheme has issue types in it that are NOT in the new scheme, but you are not using those issue types yet. 
4. The source scheme has issue types in it that are NOT in the new scheme, and you are using them

In case 1-3, JIRA will go "yup, ok".  In the fourth, it will make you choose a new issue type for all the ones that are being removed.

Inside JIRA, nothing will break, but you need to make sure it's the right thing for your actual business data.

In fact, you can be really cheeky about this - start the process, select the new scheme, and you will either get "JIRA can migrate this all automatically" (for options 1-3) or "I need you to tell me how to map the issue types" for case 4.  Both with a "cancel" button, so you can back out and re-examine your data.  Just be careful not to be too happy with the "click ok" on that screen, and it will tell you what it is planning to do without actually doing it.