What is the impact of deleting custom field context?

Question

We have some custom fields that were being used in few projects. But they are no longer required for those projects.

What happens to old issues data if i delete the context ?

What is the best practice when we create custom fields ? should we be selecting

* Global context. Apply to all issues in Jira. ?? or 
* Apply to issues under selected projects

Reason I am asking this because, when we "Bulk Change all issues", all these fields which are not used shows up in Operation Details screen.

Matt Doar_tzgiej · Answer

What Nic said.

Plus in Jira DC the existing data for a custom field in an issue is not deleted. But once a context is gone, you won't see the data again for that issue, not even in an XML dump (I think). This could be different in Cloud, but I would expect not.

I have definitely deleted a global context before and then just added a new global context and seen the data reappear. It's contexts with projects and issue types that I don't think are easy to restore. So be careful deleting those

Jyoti Mane · Answer

Thanks @Nic Brough -Adaptavist- Appreciate your response.

WHat should i do in my case then ? Those fields are no longer required in any project.

How should i get rid of those fields from "Bulk Edit Operation Details " then ??

Nic Brough -Adaptavist- · Answer

Hi Jyoti,

If you delete a project or issue type context for a field, then all the content of that field is deleted from Jira (I strongly recommend backing up before deleting or changing where a context is)

The best-practice for context is "use global fields when you are likely to want to report across projects, existing and ones you may add in the future.  Use local contexts when a field really is only for that project or issue type"

Note you'll see a lot of advice about always using limited contexts as much as possible, for performance reasons.  This does not really apply to Cloud, and changed a lot with Jira 8, it's of little impact on performance now.