The client.policy file is the J2SE policy file used by the application client. Each application client has a client.policy file. The default policy file limits the permissions of Java EE deployed application clients to the minimal set of permissions required for these applications to operate correctly. If an application client requires more than this default set of permissions, edit the client.policy file to add the custom permissions that your application client needs. Use the J2SE standard policy tool or any text editor to edit this file.
For more information on using the J2SE policy tool, see http://java.sun.com/docs/books/tutorial/security1.2/tour2/index.html.
For more information about the permissions you can set in the client.policy file, see http://java.sun.com/javase/6/docs/technotes/guides/security/permissions.html.