Solution : https://service.sap.com/sap/support/notes/592241 (SAP Service marketplace login required)
Key words : 
rtc=16 enxxmenq1377gea internal lock administration error, attached basis support package solves, active client copy processes left, 4000 completely empty client-specific tables, geg lock table overflow, global work process overview, thousand lock entries, ibm iserver iseries, attached advance correction, client copy hangs
Related Notes : 
       
| 517589 | iSeries: Client copy performance | 
| 491923 | CC RELEASE: Client copy errors in Release 6.20 | 
| 432152 | CC-RELEASE: Error in client copy in Release 6.10 |