Solution : https://service.sap.com/sap/support/notes/105429 (SAP Service marketplace login required)
Key words : 
additional key words shared memeory, extended shared memory segments, error message ora-3113, user <sid>adm, start data backups, data backup fails, offline backups work, server manager terminates, calling transaction db13, oracle program svrmgrl
Related Notes : 
       
| 710975 | FAQ: which saposcol should be used on AIX | 
| 370278 | ORA-3113 when starting SQLPLUS or SVRMGRL | 
| 203651 | Backups via DB13 with EXTSHM=ON do not work | 
| 123366 | Maximum addressable memory for the Oracle SGA | 
| 103747 | Performance: Parameter recommendations as of Release 4.0 |