Log backup failing

Hi, Our log backups are failing when the transaction volume increases. The online log shows 13:15:02 Logical Log 3614 - Backup Started 13:15:03 Logical Log 3614 Complete, timestamp: 0x283fb1f4. 13:15:04 Logical Log 3614 - Backup Aborted Aborted by client. 13:15:05 Logical Log 3615 Complete, timestamp: 0x28405ad3. 13:15:05 Logical Log 3614 - Backup Started 13:15:06 Logical Log 3614 - Backup Completed 13:15:06 Logical Log 3615 - Backup Started 13:15:08 Logical Log 3615 - Backup Aborted Aborted by client. 13:15:32 Logical Log 3615 - Backup Started 13:15:35 Logical Log 3615 - Backup Completed The onbar log shows 2009-06-17 13:15:02 8029 8028 (-43080) Process 8029 received signal 11. Process will exit after cleanup. 2009-06-17 13:15:05 8092 8091 onbar_d -b -l 2009-06-17 13:15:05 8092 8091 Begin backup logical log 3614. 2009-06-17 13:15:05 8092 8091 Successfully connected to Storage Manager. 2009-06-17 13:15:06 8092 8091 Completed backup logical log 3614 (Storage Manager copy ID: 1245258905 1245258906). 2009-06-17 13:15:06 8092 8091 Begin backup logical log 3615. 2009-06-17 13:15:06 8092 8091 ASSERT: file bar_unix.c line 1266 - contact product support 2009-06-17 13:15:06 8092 8091 See also: /opt/informix/tmp/core.8092 2009-06-17 13:15:06 8092 8091 (-43080) Process 8092 received signal 11. Process will exit after cleanup. The interesting thing is when this happens I run onbar_d -b -l -c repeatedly in interval of 30 seconds. This clears the blockage off. Please advise Thanks Chandan