Hi
The note 546006 brought me to the right direction.
The issue was in the region of security configuration which has been changed on Linux 6.
-> https://bugzilla.redhat.com/show_bug.cgi?id=432903
They introduced a default limit of maximum processes which take affect for the OS user running the brtools
The OS user <sid>adm had now a limit of 1024 maximum processes. This value is too low.
Solution
I modified the default setting in the file /etc/security/limits.d/90-nproc.conf to a proper value.
Another option is to add the unix user <sid>adm in the file /etc/security/limits.conf . As we have many installations on the same server and more are planned we make the decision to change the default one, instead of defining the limit for every user.
I'm not the OS expert. So maybe the explanation has some errors in reasoning.
regards
fabian