Hi, We have a strange thing, which not clear to us. When provisioning a new VM via REST API, if the number of vCPU for that VM is more than 16, I'm getting this error: Fault reason is "Operation Failed". Fault detail is "[Cannot add VM. Maximum number of threads per cpu exceeded]". HTTP response code is 409. Our version is: Version 4.3.6.6-1.0.9.el7 Note that manual provisioning from the UI do not produce any error when using vCPU > 16. It seems like the issue is related to this setting (from the engine): [root@olvmengine01 ~]# engine-config -g MaxNumOfThreadsPerCpu MaxNumOfThreadsPerCpu: 8 version: 4.1 MaxNumOfThreadsPerCpu: 8 version: 4.2 MaxNumOfThreadsPerCpu: 8 version: 4.3 [root@olvmengine01 ~]# But when trying to set it to another number, I'm always get this error, for example: [root@olvmengine01 ~]# engine-config -s MaxNumOfThreadsPerCpu=10 Please select a version: 1. 4.1 2. 4.2 3. 4.3 3 Cannot set value 10 to key MaxNumOfThreadsPerCpu. Questions: 1. Can you please explain why we getting this error: "Cannot add VM. Maximum number of threads per cpu exceeded"? 2. Is it related to engine-config -g MaxNumOfThreadsPerCpu? 3. Why it is working manually via the UI? 4. if its related to engine-config, why we can't set it to another number? Thanks in advance, Lavi