VDCA550 is the exam code for the VCAP5-DCA certification: (VCAP5-DCA) VMware Certified Advanced Professional 5
As it says on the page I've linked to, the exam will be retired on June 2nd.
The newer equivalent certification is the VCAP6-DCV Deploy, which has it's own exam and requirements: VMware Certified Advanced Professional 6 - Data Center Virtualization Deployment
