Solution : https://service.sap.com/sap/support/notes/727965 (SAP Service marketplace login required)
Key words : 
<dbm_password>   dbm_configset dbadtl 0            subsequent backups, terms external backup tool reason, external backup tool failed, external backup tool, dbm server crashed, dbm-api error, dbm server crash, internal sap information, internatl sap information, system displayed
Related Notes : 
       
| 669711 | Additional information about MaxDB upgrade to 7.5.00 | 
| 431508 | SAP WebAS - using DB13C or DB13 for SAP DB systems | 
| 387583 | SAP DB : Use of external backup IDs with dbmcli |