We have two independent instances of JIRA installed-system admins one instance affect other?

[Joanne]

We have two independent instances of JIRA installed, are system admins only able to perform functions that affect the instance they are admins for and not both instances?  I understand there is no risk to the other instance if they only have 'System Administrator' within their own instance as this makes sense!  But need to check as we can't have anything affecting our other instance setup.

[James Deleon]

If they're completely separate instances (which it sounds like), then the permissions will be separate for each instance. So even if John Smith has System Admin on JIRA-A, if he is just a regular user on JIRA-B, he will not be able to perform any System Admin functions on JIRA-B.