Help me! AUDITING AIX

Hi All,
i've a problem on a AIX server with audit config...

when i start the audit i receive this error:

root@****:/etc/security/audit > /usr/sbin/audit start
Audit start cleanup: The system call does not exist on this system.
** failed setting kernel audit objects

I don't understand why...
My object file seems to be OK

root@****:/etc/security/audit > cat objects
/etc/security/environ:
        w = "S_ENVIRON_WRITE"

/etc/security/group:
        w = "S_GROUP_WRITE"

/etc/security/limits:
        w = "S_LIMITS_WRITE"

/etc/security/login.cfg:
        w = "S_LOGIN_WRITE"

/etc/security/passwd:
        r = "S_PASSWD_READ"
        w = "S_PASSWD_WRITE"

/etc/security/user:
        w = "S_USER_WRITE"

/etc/security/audit/config:
        w = "AUD_CONFIG_WR"

Do you have any idea??? :wall::wall::wall::wall:

Thanks in advance.
Bye

Zio