shweta patiljadhav wrote:Do I need to give OCA before giving OCP exam?
No, that's not required! You can give both exams in random order. Although it makes sense if you take the OCA exam before the OCP exam, as the first one covers Java and OO basics while the latter one covers advanced and complex topics (generics, threads, concurrency, nio.2,...).
shweta patiljadhav wrote:Which books are recommended for OCP?
That depends on which version you want to take. Do you want OCAJP7+OCPJP7 or OCAJP8+OCPJP8? It's recommended to buy a study guide which is especially written for the version you want to take. So if you want to take the exams for Java 8, you should definitely buy a study guide covering OCAJP8 and/or OCPJP8.
shweta patiljadhav wrote:how to prepare for OCP ?
First you should decide which certification version you want to take (Java 7 or 8). And then you start preparing for the OCA certification exam using an appropriate study guide. If you have any questions about the OCA exam, you should post them in the OCAJP forum.