Rtree index creation very slow

Hi, I'm dealing with a rtree index that takes 75 hrs to get created. The table has 22M rows, nearly 2Gb data. Creating primary/foreign keys is reasonabily fast (1 - 1,5 hrs), but creating the rtree index is a nightmare and won't fit in the 12 hr. window to stop the service (as the trials ina a development machine shows - reasonabily similar boxes). I've observed that the disk isn't saturated, nor does memory (buffer pool/DSS memory). It doesn't parallel (only one CPU used, although PDQ parameters are set 'correctly'). Any hint will be appreciated! Thanks in advance. -- Jos' Luis Matute Mart'nez sending to informix-list