If a log file is backed up and all transactions within it are closed but the file is not free (status U-B-L), this logical-log file contains the most-recent checkpoint record.
To free log files with a status U-B-L, the database server must create a new checkpoint. You can execute the following command to force a checkpoint:
onmode -c
To force a checkpoint with ON–Monitor, select the Force-Ckpt option.