This is step 4 of performing a major upgrade from Enterprise Server 7 to Enterprise Server 9.2 or higher. (See a list of all steps)
Purpose of this step
Enterprise Server 9 is only compatible with InDesign Server CS6 or InDesign Server CC. In case you are using InDesign Server in your workflow, install either new version.
Steps to follow
Install InDesign Server on the available server machines by following the installation instructions as provided by Adobe.
Step 5. Upgrading Solr