Solution : https://service.sap.com/sap/support/notes/811637 (SAP Service marketplace login required)
Key words : 
undocumented br_sbq environment variable, internal database block consistency, terms br tools reason, remote tape devices, increases data integrity, gnu tape tools, secure copy command, split-mirror columns, tables/index structure, redo log files
Related Notes : 
       
| 700733 | Support for the scp command in BR*Tools | 
| 680046 | Corrections in BR*Tools Version 6.40 | 
| 378818 | Dividing the split mirrors in BRBACKUP query runs |