Use the task server to migrate a forest.

forest-migrate-with-spawn.xqy

xquery version "1.0-ml";
import module namespace ts="http://marklogic.com/xdmp/tieredstorage"
 at "/MarkLogic/tieredstorage.xqy";
 
xdmp:spawn-function(
  function() {
    ts:forest-migrate(
      xdmp:forest("my-forest"),
      xdmp:host(),
      '/media/xvdg/mldata',
      (),
      (),
      (: Make sure the timeout is long enough to copy all data.
       : Also make sure the Task Server time limit is long enough.
       :)
      ("timeout=7200")) },
  (: Must start the task in update mode, to avoid XDMP-UPDATEFUNCTIONFROMQUERY :)
  <options xmlns="xdmp:eval">
    <transaction-mode>update</transaction-mode>
  </options>)