usage space question 2 ~ Answered: amber (solid confidence) — Wolfgang Eppler's explanation (old, shorter pre-ALTER-TABLE row versions still occupying most rows, per the partition flags) matches known Informix ALTER TABLE row-versioning behavior and directly accounts for the size discrepancy; never confirmed by the OP.

Advisory only.

1, I defined below table . { TABLE "cbs".aghmx row size = 1129 number of columns = 45 index size = 140 } create table "cbs".aghmx ( zhangh char(20) not null , jioyrq char(8) not null , zhujrq char(8), jioysj integer default 0, jiaoym char(4) not null , pngzhh char(13), jiedbz char(1) not null , jio1je decimal(13,2) default 0, zhhuye decimal(15,2) default 0, yueexz char(1) not null , yueefx char(1) not null , yngyjg char(4) not null , zhngjg char(4) not null , zhyyjg char(4) not null , zhkjjg char(4) not null , jio1gy char(8) not null , shoqgy char(8), guiyls char(12) not null , yngyls char(12), xnzhbz char(1) not null , zhyodm char(22), cpznxh integer default 0, kehuzh char(20), khzhlx char(1), shunxh char(4), chbubz char(1) not null , czzpbz char(1), daynbz char(1), xuhao1 integer default 0, shjnch integer default 0, jiluzt char(1) default '0', rzzhbz char(1), dfhmnv char(200), dfzhhv char(40), dfgbdv char(3), guifhv char(12), dfhumv char(200), dfzjhv char(40), dfzzlv char(4), dfbzxv char(128), byxx01 char(60), byxx02 char(60), byxx03 char(60), byxx04 char(60), byxx05 char(60) ) with rowids fragment by expression (zhyyjg < '3109' ) in datacbs02, ((zhyyjg >= '3109' ) AND (zhyyjg < '7109' ) ) in datacbs03, ((zhyyjg >= '7109' ) AND (zhyyjg < '7702' ) ) in datacbs04, ((zhyyjg >= '7702' ) AND (zhyyjg < '8206' ) ) in datacbs05, ((zhyyjg >= '8206' ) AND (zhyyjg < '8908' ) ) in datacbs06, ((zhyyjg >= '8908' ) AND (zhyyjg < '9301' ) ) in datacbs07, ((zhyyjg >= '9301' ) AND (zhyyjg < '9413' ) ) in datacbs08, ((zhyyjg >= '9413' ) AND (zhyyjg < '9709' ) ) in datacbs09, ((zhyyjg >= '9709' ) AND (zhyyjg < '9821' ) ) in datacbs10, ((zhyyjg >= '9821' ) AND (zhyyjg < '9855' ) ) in datacbs11, (zhyyjg >= '9855' ) in datacbs12 extent size 500000 next size 200000 lock mode row; revoke all on "cbs".aghmx from "public" as "cbs"; create unique index "cbs".aghmx_idx1 on "cbs".aghmx (jioyrq,guiyls, cpznxh) using btree in idxdbs05; create index "cbs".aghmx_idx2 on "cbs".aghmx (khzhlx,kehuzh,shunxh, jioyrq,jioysj) using btree in idxdbs07; create index "cbs".aghmx_idx3 on "cbs".aghmx (zhangh,jioyrq,jiluzt) using btree in idxdbs09; create index "cbs".aghmx_idx4 on "cbs".aghmx (zhyyjg,jioyrq,daynbz, jiluzt) using btree in idxdbs10; 2. row count information > select count(*) from aghmx> ; (count(*)) 917336051 3. the output of oncheck -pt : $ oncheck -pt cbs:cbs.aghmx TBLspace Report for cbs:cbs.aghmx Table fragment partition datacbs02 in DBspace datacbs02 Physical Address 49:752688 Creation date 05/26/2011 13:20:37 TBLspace Flags 800802 Row Locking TBLspace use 4 bit bit-maps Maximum row size 1129 Number of special columns 0 Number of keys 0 Number of extents 17 Current serial value 942370755 Current SERIAL8 value 1 Current BIGSERIAL value 1 Current REFID value 1 Pagesize (k) 8 First extent size 62500 Next extent size 100000 Number of pages allocated 687500 Number of pages used 668151 Number of data pages 668068 Number of rows 25411154 Partition partnum 18874438 Partition lockid 18874438 Extents Logical Page Physical Page Size Physical Pages 0 49:158458 62500 125000 62500 81:987002 25000 50000 87500 81:1443000 25000 50000 112500 49:2503260 25000 50000 137500 49:1989032 25000 50000 162500 81:362774 25000 50000 187500 49:6905256 25000 50000 212500 49:8144278 25000 50000 237500 83:362688 25000 50000 262500 81:7471728 25000 50000 287500 81:3692552 50000 100000 337500 82:6964146 50000 100000 387500 193:912002 50000 100000 437500 194:5023998 50000 100000 487500 193:7833660 50000 100000 537500 81:6565730 50000 100000 587500 194:5623998 100000 200000 Table fragment partition datacbs03 in DBspace datacbs03 Physical Address 50:685740 Creation date 05/26/2011 13:20:37 TBLspace Flags 800802 Row Locking TBLspace use 4 bit bit-maps Maximum row size 1129 Number of special columns 0 Number of keys 0 Number of extents 31 Current serial value 1 Current SERIAL8 value 1 Current BIGSERIAL value 1 Current REFID value 1 Pagesize (k) 8 First extent size 62500 Next extent size 400000 Number of pages allocated 3587500 Number of pages used 3403091 Number of data pages 3402672 Number of rows 128321583 Partition partnum 19923110 Partition lockid 18874438 Extents Logical Page Physical Page Size Physical Pages 0 50:158458 62500 125000 62500 50:5914878 25000 50000 87500 50:6653310 25000 50000 112500 50:7138542 25000 50000 137500 50:7717374 25000 50000 162500 50:7880206 25000 50000 187500 50:8039838 25000 50000 212500 50:8226070 25000 50000 237500 84:250006 25000 50000 262500 84:579806 25000 50000 287500 84:822438 50000 100000 337500 84:1407702 50000 100000 387500 84:1876966 50000 100000 437500 84:2405830 50000 100000 487500 84:2837894 50000 100000 537500 84:3263558 50000 100000 587500 84:3686022 100000 200000 687500 84:4221350 100000 200000 787500 86:1276186 100000 200000 887500 86:2493362 100000 200000 987500 86:3333362 100000 200000 1087500 86:4040522 100000 200000 1187500 86:6486790 200000 400000 1387500 196:6 200000 400000 1587500 196:2969246 200000 400000 1787500 197:1024006 200000 400000 1987500 197:3708006 200000 400000 2187500 198:1736006 200000 400000 2387500 198:7108934 400000 800000 2787500 336:2048006 400000 800000 3187500 336:6931078 400000 800000 Table fragment partition datacbs04 in DBspace datacbs04 Physical Address 51:611988 Creation date 05/26/2011 13:20:37 TBLspace Flags 800802 Row Locking TBLspace use 4 bit bit-maps Maximum row size 1129 Number of special columns 0 Number of keys 0 Number of extents 29 Current serial value 1 Current SERIAL8 value 1 Current BIGSERIAL value 1 Current REFID value 1 Pagesize (k) 8 First extent size 62500 Next extent size 400000 Number of pag

Just a guess - because the partition flags indicate that the table was altered. Possibly the majority of rows is still stored in the old, likely much shorter, row version, thus occupying much less pages.