Hi,
IT1007 is an Object (or PD) infotype that is specific to the Position. Thus, you maintain it in PO13. However, if you have elected to use the Vacancy infotype in T77S0 - PPVAC PPVAC it will be created automatically whenever a person is terminated or transferred out of a position. Likewise, it will be delimited whenever a person is hired or transferred into a vacant position. You will get a pop-up box in either case to create or delimit the vacancy. Say "OK" and it is done.
With regards,
Venkat Polisetty.