It depends on what sort of load is there on your VM ?
mine is like this:
Oracle Unbreakable Linux --> nice and fancy name but it is customized red hat 5 linux
with 4x vCPU and 16 GB RAM and 1x e1000 vNIC
it is currently serving 15 DB instances running on medium workload without downtime. (used by less than 20 Java application servers).
all is working fine as long as you install the VMware tools in it.
What about openSuse11 with Oracle11? I have a problem with performance, my vCPUs are about 100% utilized...
its look like on DATA Base VM you need to to configure the I/O share on Disks or/And VM disks Share ,and some time using RDM disks will be usefull .
Last year I went to the UK Oracle user group conference where one of the speakers did some comparisons with running oracle on a vm against running it on a physical machine.
The consensus was that the performance was significantly worse when running in a vm to that of physical hardware. If you start swapping then you can forget it as you have two swap file contending with each other, the vmware one and the OS one.
We run over 100 vms, but none of these are for Oracle, and I don't intend changing this anytime soon.
I could possibly entertain it in a dev/uat environment, but I would seriously question doing it in production!