Lucene has a number of properties that can be tuned. They can be adjusted either programmatically, using the Lucene API, or their default values can be set via system properties (only up to including Lucene 1.4) described in this document. Starting with Lucene 1.9, the system properties are not supported anymore and the API (i.e. the get/set methods) should be used directly.

Lucene Property	System Property	Default Value
mergeFactor	org.apache.lucene.mergeFactor	10
minMergeDocs	org.apache.lucene.minMergeDocs	10
maxMergeDocs	org.apache.lucene.maxMergeDocs	Integer.MAX_VALUE
maxFieldLength	org.apache.lucene.maxFieldLength	10000
COMMIT_LOCK_TIMEOUT	org.apache.lucene.commitLockTimeout	10000 ms
WRITE_LOCK_TIMEOUT	org.apache.lucene.writeLockTimeout	1000 ms
maxClauseCount	org.apache.lucene.maxClauseCount	1024
lockDir	org.apache.lucene.lockDir	the value of java.io.tmpdir system property
FSDirectory.class	org.apache.lucene.FSDirectory.class	org.apache.lucene.store.FSDirectory
SegmentReader.class	org.apache.lucene.index.SegmentReader.class	org.apache.lucene.index.SegmentReader