How to upgrade splunk from 6.3.1 to latest version without downtime?

[mohanbabusplunk]

Planning to upgrade splunk enterprise from 6.3.1 to latest version.
Is there a way to do it without downtime?
1. We have indexer cluster and search cluster and both are integrated.
2. We have Es app 4.0.0. installed in search heads.
Kindly help me with the upgrade paths with no downtime.

[sloshburch]

Check the new rolling upgrade features within the documentation. Although they may not be available in 6.3.1.