Understanding Jira Schema

[Mosh]

Hello
I'm now evaluating Jira. Forgive me if I'm asking a question of beginners.

I created two projects and it seems they're both based on the same schema.
Now, if I want to change one of the projects (e.g. set a new field), it also affects the other project.
So how should I change one project only? What's the best practice?
Actually I'd like to isolate the project schemas so I can change one separately. In a similar tools (like Rational ClearQuest\ RTC) we used to create two separated schema.

This leads to another question: what if I want to test the changes before it affects all users?
In other tools I can set a test database so I can all my changes on a separated testing environment before putting it into production.
Please advice and let me know the best practices.

THANK YOU!

[Andy Brook]

JIRA's Custom Fields can be scoped via Contexts through entities like the Project (so it only appears in X rather than Y) and IssueType, or even Screens within workflows.

• https://confluence.atlassian.com/display/JIRA060/Configuring+a+Custom+Field

JIRA hasn't got a facility to 'dry run' that kind of configuration, to test things before the affect everyone, use a separate Test instance.  Commercially licensed customers can generate a Developer license from the https://my.atlassian.com Production License, you're free to create any number of non-production instance just testing just like that.