Where did you read anything about a 2G heap being “in the danger zone”? I
routinely see heap sizes in the 16G range and greater. The default 512M is
actually _much_ lower than it probably should be, see:
https://issues.apache.org/jira/browse/SOLR-13446
The “danger” if you allocate too much memo
I think you can safely increase heap size to 1 gb or what you need.
Be aware though:
Solrs performance depends heavily on file system caches which are not on the
heap! So you need more memory than what you configure as heap freely available.
How much more depends on your index size.
Another opt
