You can use the LIST UTILITIES command to monitor the progress of backup operations on a database.
list utilities show detail
For backup operations, an initial estimate of the number of bytes to be processed will be specified. As the backup operation progresses the number of bytes to be processed will be updated. The bytes shown does not correspond to the size of the image and should not be used as an estimate for backup image size. The actual image might be much smaller depending on whether it is an incremental or compressed backup.
ID = 3
Type = BACKUP
Database Name = SAMPLE
Partition Number = 0
Description = offline db
Start Time = 08/04/2011 12:16:23.248367
State = Executing
Invocation Type = User
Throttling:
Priority = Unthrottled
Progress Monitoring:
Extimated Percentage Complete = 31
Total Work = 123147277 bytes
Completed Work = 37857269 bytes
Start Time = 08/04/2011 12:16:23.248377