Bad performance with large spool file when job is rerun.
1) First of all, MoM will use TCP PBS_BATCH_MvJobFile requests so move the files over to the server. Sadly, it will do so in extremely small requests that only contain a chunk of RT_BLK_SZ bytes from the file.
2) The server likewise uses TCP to send back the spool files to the new MoM when it runs a new runversion of the job. That, too, uses very small blocks (SCRIPT_CHUNK_Z) that each generate an interserver message with a PBS_BATCH_MvJobFile request.