how to refresh datatable in JSf with session bean?

I have a Session Managed Bean where I have a list that I show in datatable and when I click in button I change the list in the managed bean but the table didnt change in the JSF page :

<p:commandButton id="someId" value="Button" action="#{gestionduplanning.exec2()}">
    <f:ajax  render="koka"/>
</p:commandButton> 

<p:dataTable id="koka" var="op" value="#{gestionduplanning.listop}" style="width: 700px;float: left;">
    <p:column headerText ="operateur" style="width:50px;" >       
        <h:outputText value="#{op.operateur.matricule}"/>
    </p:column> 
</p:dataTable>

How can I update the table in JSF and I need to keep my managed bean as session bean?

Solution

Remove <f:ajax render="koka"/> and add update="koka" to your <p:commandButton

<p:commandButton update="koka" id="someId" value="Button" action="#{gestionduplanning.exec2()}"/>

Also you better don't nest f:ajax with inside Primefaces components and vice versa...

f:ajax is meant to use with native JSF components

p:ajax is meant to use with PrimeFaces components

It is fine to have both , Primefaces components and JSF native components in one page, just make sure to use p:ajax in Primefaces components and f:ajax in JSF native components