We are looking to upgrade from Apache Solr 4.7.2 to ApacheSolr 7.6. The documentation is not very clear. Please reply with your valuable notes
Thanks in advance
No. As seen on the reference page for the Index Upgrader tool:
Indexes can only be upgraded from the previous major release version to the current major release version.
This means that the IndexUpgrader Tool in any Solr 7.x release, for example, can only work with indexes from 6.x releases, but cannot work with indexes from Solr 5.x or earlier.
If you are currently using an earlier release such as 5.x and want to move more than one major version ahead, you need to first upgrade your indexes to the next major version (6.x), then again to the major version after that (7.x), etc.
There's also an indexupgrader tool that attempts to perform this sequence automagically for you from your current version.