If a large XML import fails, try this fix, from user K.B.:
Recently I found that my weekly import of a large XML file of notes failed with the error:
Cannot Import Vault 3 File. JAXP000100002: The length of entity "[xml]" is "100,001" that exceeds the "100,000" limit set by "jdk.xml.maxGeneralEntitySizeLimit".
Fortunately, I could fix that by changing my shortcut to increase two limits from their defaults of 100000 to 200000:
-Djdk.xml.maxGeneralEntitySizeLimit=200000 -Djdk.xml.totalEntitySizeLimit=2000000