how to solve this exception in Neo4j? - exception

Question

thanks for reading my problem,may you help me to solve this problem.
at first time,it will be ok,but when it finish, I do the same thing,It occurped this exception:
org.neo4j.graphdb.TransactionFailureException: Database is currently not available. No blocking components
at org.neo4j.kernel.InternalAbstractGraphDatabase.beginTx(InternalAbstractGraphDatabase.java:942)
at org.neo4j.kernel.TransactionBuilderImpl.begin(TransactionBuilderImpl.java:43)
at org.neo4j.kernel.InternalAbstractGraphDatabase.beginTx(InternalAbstractGraphDatabase.java:935)
at com.myapplication.dao.DataOperation.getUser(DataOperation.java:77)
at com.myapplication.dao.DataOperation.createRelationShip(DataOperation.java:205)
at com.myapplication.business.UploadData.upload(UploadData.java:29)
at com.myapplication.servlet.UploadServlet.doPost(UploadServlet.java:96)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1852)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
but all my operations to change the database are in a transction like demo
try (Transaction tx = graphDB.beginTx()) {
//do something
tx.success();
}
How do I use Neo4j connections like MySQL connections?
my environment is Eclipse + Tomcat 7.0 in Java 7
and this is the link of database log https://www.dropbox.com/s/a7858mywidbvr03/messages.log
thank you very much