hanging request for an update using Hibernate and Mysql

hi everyone.
i'm using Hibernate,mysql and DS for so many tables and it works fine for CRUD , i have a problem with just one table when i try to update records , the request is hanging so long before it works , i don't know what's wrong , here some code that can help.

<hibernate-mapping>
<class name="com.sample.Marking" table="marking">
<id name="markingId" type="java.lang.Integer">
<column name="markingId" />
<generator class="increment" />
</id>
<many-to-one name="users" class="com.sample.Users" fetch="select">
<column name="userId" not-null="true" />
</many-to-one>
<many-to-one name="offre" class="com.sample.Offre" fetch="select">
<column name="offreId" not-null="true" />
</many-to-one>
<property name="marked" type="java.lang.String">
<column name="marked" length="1" not-null="true" />
</property>
<property name="reserved" type="java.lang.String">
<column name="reserved" length="1" not-null="true" />
</property>
</class>
</hibernate-mapping>


public function reserv():void{
CursorManager.setBusyCursor();
var param:Array = new Array;
param.push(offreIdFill);
param.push(userIdFill);
reserveMarking.addEventListener(CollectionEvent.COLLECTION_CHANGE,refreshReserv);
token = markingHibernateService.fill(reserveMarking,"flex:hql","from Marking m where m.offre = ? and m.users = ?",param);
token.action = "reserv";
}
public function refreshReserv(event:CollectionEvent):void{
if(reserveMarking.length == 1){
mark = reserveMarking.getItemAt(0) as Marking;
}
}

private function resultHandler(event:ResultEvent):void{
if(event.token.action == "reserv"){
mark.reserved = "y";
markingHibernateService.commit();
CursorManager.removeBusyCursor();
Alert.show("offer reserved with succes","info");
}
}

<mx:DataService id="markingHibernateService" autoCommit="true" destination="markingHibernate" result="resultHandler(event)"/>

i hope it can help. thx