Solution : https://service.sap.com/sap/support/notes/82634 (SAP Service marketplace login required)
Key words : 
symptom ora-01555ora-01626 additional key words rollback segments, solution sqldba lmode=yconnect internal spool rollback, rollback segments, spool offsend, analyzing problems, outselect usn, select  initial_extent, tablespace_namefrom dba_rollback_segs, generated file, prerequisites
Related Notes : 
       
| 60233 | Oracle rollback segments, more information. | 
| 40024 | Transferring customer files to sapserv# using ftp | 
| 3807 | Error messages regarding rollback and undo segments |