Solution : https://service.sap.com/sap/support/notes/1524186 (SAP Service marketplace login required)
Key words : 
ehp <number>sps<number>-> support package stack guideupdate procedure log, /instguides-> installation & upgrade guides-> sap netweaver-> sap netweaver 7, support packages stack guide, -> maintenance-> sps <number>, fixed sporadic nameserver crashes, fixed misleading errors reported, installation script 'install, fix program errors, existing bwa720 instance, mfdownload procedurefor details
Related Notes : 
       
| 1534565 | BWA 7.20 Rev. 07: AlertServer corrections and hints | 
| 1522036 | BWA 7.20: Index creation fails | 
| 1517586 | BWA 7.20 Rev 6: AlertServer corrections and hints | 
| 1445787 | BWA 7.20 License Key Installation | 
| 1393505 | BWA 7.20: Central Note | 
| 1392570 | BWA 7.20: Installation | 
| 1392526 | BWA 7.20: Update | 
| 1058533 | TREX/BWA/HANA service connection to customer systems | 
| 1021236 | Linux: Using SAP Kernel 7.01 and higher on RHEL4 and SLES9 |