Extremly long checkpoints: How to find the reason and solve the problem (7.31 FD3)

Hello, we have some serious problems with extremly long checkpoints. Interactive users can't really work. 09:01:15 Logical Log 28452 Complete 09:01:16 Logical Log 28452 - Backup Started 09:01:36 Logical Log 28452 - Backup Completed 09:30:28 Checkpoint Completed: duration was 1465 seconds. 09:30:28 Checkpoint loguniq 28453, logpos 0x2ac60 09:43:43 Checkpoint Completed: duration was 495 seconds. 09:43:43 Checkpoint loguniq 28453, logpos 0x2b96018 09:50:50 Checkpoint Completed: duration was 126 seconds. 09:50:50 Checkpoint loguniq 28453, logpos 0x2cdc018 09:57:03 Checkpoint Completed: duration was 73 seconds. 09:57:03 Checkpoint loguniq 28453, logpos 0x32c1018 10:04:05 Checkpoint Completed: duration was 122 seconds. 10:04:05 Checkpoint loguniq 28453, logpos 0x3df4018 How can i find the reason for the checkpoints and solve the problem? I know that some users are starting calculating jobs which will delete/write about 500000 rows within one transaction maximum. There are also using a lot of temp tables and do insert/updates within the temp tables. Greetings, J'rg