Solution : https://service.sap.com/sap/support/notes/836947 (SAP Service marketplace login required)
Key words : 
end  'sapdb1'  'sapxirun'  'sapxirep'  'sapxidir'  'sapbxidb', exclusively ascii application servers, db1> sql_execute select username, admin       > sql_execute select username, select returns table names, control -usql sapdb1, control -usql sapbxidb, db1> sql_connect superdba, <dbm_user_password>       > sql_connect superdba, <dbm_user_password>        -usql <sql_user>
Related Notes : 
       
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| 490325 | Additional info on upgrade to SAP Web AS 6.20 SAP DB/MaxDB |