Please help: problem with index

Dear Informix Gurus, I have a problem with deleting old data (last 1 day's data from 300 stored days) from the most important table of our system. In online.log there are the following messages: 04:00:47 Assert Failed: Fragid 0x500002, Rowid 0x2ba4b002 not found for delete in partnum 600009 04:00:47 Informix Dynamic Server 2000 Version 9.21.HC4 04:00:47 Who: Session(1042796, cortex@strong, 14976, -1215118544) Thread(1048556, sqlexec, b79140ec, 1) File: exfmsupp.c Line: 853 04:00:47 Results: Delete failed 04:00:47 Action: Run 'oncheck -cI cortex:"cortex".tlog#tlog_acbalref' 04:00:47 stack trace for pid 17705 written to /ctxtools/informix/af.3d4da3f 04:00:47 See Also: /ctxtools/informix/af.3d4da3f, shmem.3d4da3f.0 04:01:02 Error writing '/ctxtools/informix/shmem.3d4da3f.0' errno = 28 04:01:02 Process exited with return code 127: /bin/sh /bin/sh -c /ctxtools/informix/etc/alarm_prog.sh 4 2 "Index failure: 'cortex:"cortex".tlog#tlog_acbalref'." "Fragi Oncheck did not help: oncheck -cI cortex:tlog#tlog_acbalref Validating index tlog_acbalref for cortex:cortex.tlog... Index tlog_acbalref Index fragment in DBspace tlogidx ERROR:No btree item exists for data row. Fragid 0x500002 Rowid 0x2ba4b001 contains key value: Key: "":" ":37435: Please Drop and ReCreate Index tlog_acbalref for cortex:cortex.tlog. The problem is that this table is very large (about 10 milions records) - recreating index will take long time and we cannot stop our system for so long time. Could you please advise me what else can I do except drop/create index? Thank you in advance. Best regards. -- Nadezda Boltach