Hi Chen, I cannot say that I have seen a big jump in space like you have, I did come across an old bug reference 5987262 , but that was for a 9.2 release. I came across you post trying to figure out what dba_hist_seg_stat is about. I cannot even make sense of column values in the same row for a table! On the database I am querying it, for a standard 8 day AWR baseline, more space is reported as being used as than has been allocated, when I sum up the appropriate columns for the snapshots. It appears to me that the way Oracle calculates these values and stores them does not make this view of much use. Note 788892.1 repeats the advice you were given. Regards Pete -- //www.freelists.org/webpage/oracle-l