Accepted Solutions
Sorry, I'm not an Oracle licensing expert 
This Oracle licensing FAQ may help you though: http://www.orafaq.com/wiki/Oracle_licensing
I think you could take the Oracle Standard One maybe? Though it is restricted to only 2 CPU sockets, so if you ever want more CPUs, you'll need to buy another license.
The documentation doesn't say it's not supported ... This doesn't mean it's a supported feature though, I guess the only way to find out is to test it and let us know so other people might benefit from it
The documentation states:
The following features are not supported by the VMware vCenter Server Appliance.
Microsoft SQL Server as a supported local or remote database
And that's it ... Nothing about Oracle Express ... The question you need to ask yourself is, is Oracle Express the right choice?
What are the limits of Oracle Express, didn't it used to be that Oracle Express can only use 1GB RAM? That would not be interesting when your vSphere environment grows ... Maybe for a very small lab yes ... But then you might as well use the embedded DB (unless you want to play around with Oracle of course).
Thank you. We dont use Oracle in our company, so I dont know about limits... Thanks.
uffff.... because we will have 100++ VMs we must use Oracle. But why I must buy 5 licence as minimum 
. Any idea how buy only one?:)
Sorry, I'm not an Oracle licensing expert
This Oracle licensing FAQ may help you though: http://www.orafaq.com/wiki/Oracle_licensing
I think you could take the Oracle Standard One maybe? Though it is restricted to only 2 CPU sockets, so if you ever want more CPUs, you'll need to buy another license.