Grigori,
Thank you for your analysis.
TSM Support says, "the entire systemstate does not follow the incremental, but
rather the System Writer component of the system state will use the progressive
incremental operations. All other writers will still perform full backups. See
the Client Manuals for details:
http://publib.boulder.ibm.com/infocenter/tsminfo/v6r2/topic/com.ibm.itsm.client.doc/r_cmd_bkupsystemstate.html
Best wishes to all,
Keith Arbogast