Solution : https://service.sap.com/sap/support/notes/183791 (SAP Service marketplace login required)
Key words : 
start transaction st04 --> detailed analysis menu --> oracle session, additional key words psaptemp, event 'sort write request', edit --> filter session, sort write request, oracle internal processes, work processes hang, flag 'active sessions, -ts> coalesce caution, load database data
Related Notes : 
       
| 659946 | FAQ: Temporary tablespaces | 
| 432377 | ODMA modifies Storage settings for Temporary TS | 
| 416772 | General tablespace types, temporary tablespace parameters | 
| 216881 | SMON process slowly deletes temp. segments PSAPTEMP | 
| 216440 | Condensor: ORA-2195 when summarizing InfoCubes | 
| 164925 | Storage parameter of tablespace PSAPTEMP | 
| 124106 | SMON - Temp Segment Cleanup and Free Space Coalesce | 
| 78595 | ORA1575 timeout waiting for space management res. |