Hi, based on Daniels example from:
http://blog.miconda.eu/2010/01/best-of-new-in-kamailio-300-19-htable.html

...
modparam("htable", "htable", "acalls=>size=8;")
...
route {
 ...
 if(is_method("INVITE") && !has_totag())
 {
      # a new call
      if($shtcv(ht=>^$fU$)>=3)
      {
          send_reply("403", "limit exceeded");
          exit;
      }
      $sht(acalls=>$ci) = $fU;
      t_on_failure("NEW_INVITE");
 }

 if(is_method("BYE"))
 {
    $sht(acalls=>$ci) = $null;
 }
 ...
}

failure_route[NEW_INVITE] {
  $sht(acalls=>$ci) = $null;
}

I use this htable variant to share data between two dialogs (store Contact from one dialog, and re-write other R-URI with it). Referenced by call-id:

...
$avp(referenceID) = $ci + "-" + $avp(direction);
$sht(a=>$avp(referenceID)) = $ct;
...
...

$avp(referenceID) = $ci + "-" + $avp(direction);

avp(newru) = $sht(a=>$avp(referenceID));
avp_subst("$avp(newru)", "/(<)(.*)(>)/\2/");
xlog("L_NOTICE", ">>>>>>>>  ReWrite ru with:$avp(newru)\n");
$ru = $avp(newru);
...

Is this the best method to share data between two dialogs? Because you have to take
care yourself with failure_route and so on, to free (set back to $null) them. Or is there
a more elegant way for that task?