The Oracle E-Business Suite R12.1 Purchasing Essentials Exam indicates a functional foundation in E-Business Essentials including skills such as how to access and navigate within the R12 E-Business Suite, how to enter data, retrieve information in the form of a query and access online help.
Candidates must also demonstrate knowledge of Setting up and using Oracle Purchasing, Applying document security, Creating requisitions and purchase orders, applying routing and approval methods, Entering and managing receipts and using the Professional Buyer's Work Center.
Clearing the Certification will not automatically lead you to a job. However a Certification with some project experience will certainly open a lot of doors for you. The consultants who will benefit the most from a certification are the ones with typically less than 2 year's project experience.
This is not to say that consultants with higher experience will not benefit, but at that level, having a certification matters much less. So if you have little or no Oracle Purchasing experience, you should get yourself certified, get some project experience, and then the whole of the Oracle applications World is open for you to explore.
Helping you with the first step on you ladder to success is this book