Translations:API/31/en
From ArdorDocs
Prunable data can be preserved on a node beyond the predetermined minimum lifetime by setting the nxt.maxPrunableLifetime property to a larger value than two weeks or to -1 to preserve it indefinitely. To force the node to include such preserved prunable data when transactions and blocks are transmitted to peer nodes, set the nxt.includeExpiredPrunables property to true, thus making it an archival node.