setProperty(propertyName, value) - JPA EntityManager's method

void setProperty(
  String propertyName,
  Object value

Set an entity manager property or hint. If a vendor-specific property or hint is not recognized, it is silently ignored.
propertyName - name of property or hint
value - value for property or hint
IllegalArgumentException - if the second argument is not valid for the implementation
JPA 2.0

This documentation page is derived (with some adjustments) from the open source JPA 2 RI (EclipseLink)
and is available under the terms of the Eclipse Public License, v. 1.0 and Eclipse Distribution License, v. 1.0.
Object Relational Mapping (ORM) JPA 2 providers include Hibernate, EclipseLink, TopLink, OpenJPA and DataNucleus.
ObjectDB is not an ORM JPA implementation but an Object Database for Java with built in JPA 2 support.