Since we are trying to move from TSM to IASP , the TSM storage sets are in TSM servers, where as the IASP storage sets were in iSeries. So, we cannot do the above option.
Currently, we are planning to change the storage sets by logging to OnDemand Admin ->update the application group(to something like Appgrp_old), copy the Appgrp_old to new Appgrp -> select the new IASP storage set and change all the applications attached to the new app group .
lot of manual work!! Please help