Never ending Checkpoint

IDS 9.40.FC4W2 SunOS 5.8 Last Saturday we had a "never ending checkpoint". There are no loggings about the event except the lines in online.log: 11:41:01 Fuzzy Checkpoint Completed: duration was 2 seconds, 2789 buffersnot flushed, timestamp: 0x60364810. 11:41:01 Checkpoint loguniq 1497261, logpos 0x18a94d4, timestamp:0x60364810 11:41:01 Maximum server connections 358 11:41:09 Logical Log 1497261 Complete, timestamp: 0x6036ed0c. 11:41:43 Logical Log 1497262 Complete, timestamp: 0x603a11fd. 11:41:45 Logical Log 1497243 - Backup Started 11:41:54 Logical Log 1497243 - Backup Completed 11:41:54 Logical Log 1497244 - Backup Started 11:41:57 Logical Log 1497244 - Backup Completed 11:41:57 Logical Log 1497245 - Backup Started 11:42:00 Logical Log 1497245 - Backup Completed 11:42:00 Logical Log 1497246 - Backup Started 11:42:03 Logical Log 1497246 - Backup Completed 11:42:03 Logical Log 1497247 - Backup Started 11:42:06 Logical Log 1497247 - Backup Completed 11:42:06 Logical Log 1497248 - Backup Started 11:42:10 Logical Log 1497248 - Backup Completed 11:42:10 Logical Log 1497249 - Backup Started 11:42:13 Logical Log 1497249 - Backup Completed 11:42:13 Logical Log 1497250 - Backup Started 11:42:16 Logical Log 1497250 - Backup Completed 11:42:16 Logical Log 1497251 - Backup Started 13:45:54 Process exited with return code 137: /bin/sh /bin/sh -c /opt/lib/informix/etc/log_full.sh 2 23 "Logical Log 1497262 Complete, timestamp: 0x603a11fd." "Logical 14:26:23 WARNING: Checkpoint appears stalled and may not complete before the database server shuts down. 14:31:51 IBM Informix Dynamic Server Started. At 14:26:23 the server was shut down an onmode -ky and then startet with oninit. The "checkpoint request" lasted nearly three hours yet. I tried to find helpful advices in c.d.i about long lasting checkpoints and return code 137 but couldn't find anything that gives me an answer. Thanks in advance, Reinhard.