This is a quick blog post to help folks that are testing with SLOB at high user (session) counts. The situation may arise where you are testing SLOB on a large configuration, with or without SQL*Net, and the SLOB driver (runit.sh) is failing to produce Automatic Workload Repository (a.k.a AWR) reports.
This problem will generally be seen on RHEL 6 variants that implement the much maligned /etc/security/limits.d/90-nproc.conf method of preventing fork bombs. For more information on this configuration file please refer to Red Hat bug 919793.
If you are not getting AWR reports under the condition I describe then the problem is most likely due to 90-nproc.conf short circuiting the ulimit(3) tuning you’ve established.
As an example remedy, please consider the following settings I recommended to my colleagues at VCE for performance testing of the vBlock Specialized System for High Performance Databases: