onstat -P shows high percentage of other pages

Hello, we switched recently from IDS.7.31.FD2 to IDS.940.FC5. We have 16000000 BUFFERS configured (16 Mio). 48 minutes after a database restart onstat -P showed the following BUFFER usage: Data 36.83 Btree 22.21 Other 40.96 The 40.96% other were not unused pages (partnum 0), but most of them belonged to two indices of a large fragmented table: partnum total btree data other dirty 12582998 2927190 4926 0 2922264 40 12582999 3374545 57185 0 3317360 211 After 2 hours and 39 minutes the BUFFER usage changed to: Data 32.63 Btree 44.46 Other 22.91 partnums of a large fragmented table/index: partnum total btree data other dirty 12582998 330928 3 0 330925 0 12582999 2715629 3 0 2715626 0 After 3 hours Other dropped to 18.55% . Has anyone seen this behaviour before? What 'other' pages should that be? The difference between allocated and used pages for these indices is much less than 3 Mio pages each. May this point to some issue with the new btree scanners? At the moment we run 3 scanners with priority low, threshold 10000 and rangesize 500. Regards, Andreas Kutsche