Splunk's response.
As per the case description, I understand that all your splunk instances are running on 6.3.0 version and you want to upgrade your Cluster master/license master/Deployment server to 6.5 version.
I believe your indexers are in cluster mode and a single splunk instance is acting as "Cluster master/license master/Deployment server". Please correct me if I am wrong.
First you can upgrade your Cluster master/license master/Deployment server(from 6.3 to 6.5 version). The cluster master and cluster peers can be on different versions but the version of the cluster master should be higher than the cluster peers(indexers).
So in your environment all the splunk instances are on 6.3 version, if you upgrade the cluster master to 6.5 version, there will be no compatibility issue.
Please refer the below link:
http://docs.splunk.com/Documentation/Splunk/6.5.3/Indexer/Systemrequirements#Splunk_Enterprise_version_compatibility
We recommend a dedicated splunk instance for cluster master. For better functioning and performance of cluster master, we suggest you to deploy an another splunk instance for deployment server and License master.
Note:
As a support team, we recommend you to get all your splunk instances to the same version.
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