JIRA Datacenter will automatically keep all the copies of the index up to date automatically. This synchronisation is not fully synchronous, but aims for eventual consistency. This means that there is some delay before index changes are seen on other nodes in the cluster.
Each indexing operation writes a row to the database table replicatedindexoperation. All of the nodes then look for entries in this table that were inserted by nodes other than themselves. They then apply the changes to their local Lucene index by recollecting the CF values and recreating Lucene document.
see Lucene Index Synchronization in Jira Data Center for more details.
Replicate Lucene document between nodes (Document-based replication - DBR).
Thus reduce overhead to recollect the CF values and recreate Lucene document.