how to add buffer via TP
tp addtobuffer P28KT00687 pf=TP_DOMAIN_D28.PFL D28
tp import P28KT00687 D28 client300 pf=TP_DOMAIN_D28.PFL U128

Check status of the transport
/usr/sap/trans/tmp
tail -f P28IT00687.D28

You may also user ps -ef|grep tp