Solution : https://service.sap.com/sap/support/notes/572060 (SAP Service marketplace login required)
Key words : 
concerns releasing occupied memory space, long data archiving deletion runs, affects newly allocated extents, 192 bytes - 150 bytes administration data - 10% pctfree, 64k start extent size, chronologically sorted document number, half-filled data blocks, partially filled blocks remain, data archiving deletion run, sales document flow
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| 821687 | FAQ: Space utilization and fragmentation in Oracle | 
| 766827 | Composite SAP note: Performance SCM 4.0 | 
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| 592393 | FAQ: Oracle | 
| 409376 | Use of locally managed tablespaces for SAP R/3 | 
| 214995 | Oracle locally managed tablespaces in the SAP environment | 
| 105047 | Support for Oracle functions in the SAP environment |