Backup I/O 
In the I/O Operations user menu of the DBA Cockpit you can find, among other things, a display of read and write accesses during a backup.
Procedure
Open the DBA Cockpit (transaction code DBACOCKPIT) and select 
Performance 
I/O Operations Backup I/O 
.
You can refresh the display. To do so, choose Edit Refresh .
You can automate this function by choosing Edit Automatic Refresh On/Off . The display for the function for the automatic refresh is above the header line of the table (green symbol: on, red symbol: off). In the field next to this, you can specify the time interval with which the automatic refresh should take place. The default value is 5 seconds.
Result
The system displays the number of read and write accesses on the individual volumes caused by a currently running backup action. An access corresponds to an I/O operation. This includes multiple pages, though the number can vary.
You can see the actual number of backed up pages in the column Saved Pages (Backup).
This means that you can use the Backup I/O display to monitor the asynchronous I/O operations caused by backups. You can refresh the display during a running backup, and in this way obtain a display of the progress of the backup run.