Index building issue on multi nodes

Issue

The development env and architecture as below:
JBoss EAP 6.3.0+JDG Server 6.4.1 Module *3(3 node)
Cache Store:async,Oracle DB
Cluster mode:dist
infinispan setting as below:

<namedCache name="Example_G3">      
        <clustering mode="dist">            
            <sync></sync>
            <l1 enabled="false" lifespan="0" onRehash="false"></l1>
            <hash numOwners="2"></hash>
            <stateTransfer fetchInMemoryState="true"></stateTransfer>           
        </clustering>                   
        <jmxStatistics enabled="true"></jmxStatistics>
        <eviction maxEntries="16384" strategy="LRU" ></eviction>        
        <persistence passivation="false">
            <stringKeyedJdbcStore xmlns="urn:infinispan:config:jdbc:6.0"  fetchPersistentState="false" ignoreModifications="false" purgeOnStartup="false">
                <dataSource jndiUrl="java:jboss/datasources/DS_Example" ></dataSource>              
                <stringKeyedTable dropOnExit="false" createOnStart="true" prefix="JDG">
                    <idColumn name="id" type="VARCHAR2(200)" ></idColumn>
                    <dataColumn name="datum" type="BLOB" ></dataColumn>
                    <timestampColumn name="version" type="NUMBER" ></timestampColumn>                   
                </stringKeyedTable>
                <async enabled="true" ></async>
            </stringKeyedJdbcStore>         
        </persistence>
        <indexing enabled="true">           
            <properties>
                <property name="hibernate.search.default.directory_provider" value="filesystem" ></property>
                <property name="hibernate.search.default.indexBase" value="/jdg_index" ></property>             
                <property name="hibernate.search.default.exclusive_index_use" value="false" ></property>                
                <property name="hibernate.search.default.worker.execution" value="async"></property>
                <property name="hibernate.search.default.worker.thread_pool" value="10"></property>
                <property name="hibernate.search.default.worker.buffer_queue_max" value="10000"></property>
                <property name="hibernate.search.default.indexwriter.merge_factor" value="30" ></property>
                <property name="hibernate.search.default.indexwriter.merge_max_size" value="2048" ></property>
                <property name="hibernate.search.default.indexwriter.ram_buffer_size" value="256" ></property>              
                <property name="hibernate.search.default.lucene_version" value="LUCENE_36"></property>                                      
            </properties>
        </indexing>                                     
    </namedCache>

when the cache is buiding the index, the below ERROR message occured:

00:40:37,755 ERROR [org.hibernate.search.backend.impl.lucene.LuceneBackendQueueTask] (Hibernate Search: Index updates queue processor for index Snapshot-1) HSEARCH000072: Couldn't open the IndexWriter because of previous error: operation skipped, index ouf of sync!