public Properties getPersistenceCustomProperties() {
    if (null != customPersistenceProperties) {
      return customPersistenceProperties;
    }

    customPersistenceProperties = new Properties();

    for (Entry<Object, Object> entry : properties.entrySet()) {
      String key = entry.getKey().toString();
      String val = entry.getValue().toString();
      if (key.startsWith(SERVER_PERSISTENCE_PROPERTIES_PREFIX)) {
        key = key.substring(SERVER_PERSISTENCE_PROPERTIES_PREFIX.length());
        customPersistenceProperties.put(key, val);
      }
    }

    return customPersistenceProperties;
  }
Gets all properties that begin with
{@value #SERVER_PERSISTENCE_PROPERTIES_PREFIX} , removing the prefix. These
properties are used to pass JPA-specific properties to the persistence
provider (such as EclipseLink).
<p/>
server.persistence.properties.eclipselink.jdbc.batch-writing.size=25 ->
eclipselink.jdbc.batch-writing.size=25

@return custom properties for database connections
ambari-server/src/main/java/org/apache/ambari/server/configuration/Configuration.java