In a production environment, verify that the total virtual CPU resources for the virtual machines do not exceed the CPU capacity of the host machine. That is, the total number of CPUs for the virtual machine cannot exceed the CPU capacity of the physical machine.
Sybase recommends that you undercommit CPU resources on the host machine; if the host CPU capacity is overloaded, the virtual database performance may degrade. Never overcommit CPU resources in a production environment.
A reasonable upper limit for CPU resources is about 80 percent of consumption. Sybase recommends that you create an alert to be sent to the virtual infrastructure administrator when CPU resources reach 90 percent of consumption.
Multithreaded applications like Adaptive Server may benefit from using multiple CPUs. To ensure that the physical CPUs are not oversubscribed, limit the total number of virtual CPUs to the total number of physical CPUs minus 1.
Configuring virtual Adaptive Servers with excess virtual CPUs can impose a small resource requirement on vSphere because unused virtual CPUs continue to consume timer interrupts. vSphere coschedules virtual CPUs and attempts to run the virtual CPUs in parallel whenever possible. Unused virtual CPUs impose scheduling constraints on the used virtual CPUs and might degrade performance.