Hi Samba,
Also can you please let us know how many MAX_CPU,CacheMemorySize MAXUSERTASKS you have defined for the DB.
Also have look on below oss note for performance issues & Parameter recommendations:-
1006491 - MaxDB on Linux (NUMA): Performance problems with MAXCPU > 1
1308217 - SAP MaxDB 7.8 database parameter recommendations
Regards,
Ram