n-NULL values for input arguments <i>import_global_ids</i>, <i>import_local_ids</i>, <i>import_procs</i>, and <i>import_to_part</i> are optional.  
The values must be non-NULL only if no export lists are provided or if
the import lists are used by the application callback functions 
<a href="ug_query_mig.html#ZOLTAN_PRE_MIGRATE_PP_FN"><b>ZOLTAN_PRE_MIGRATE_PP_FN</b></a>,
<a href="ug_query_mig.html#ZOLTAN_MID_MIGRATE_PP_FN"><b>ZOLTAN_MID_MIGRATE_PP_FN</b></a>, and 
<a href="ug_query_mig.html#ZOLTAN_POST_MIGR