I am not familiar with EBS but , from oc4j point of view there is no upgrade as such from 10.1.2 release to 10.1.3
Both are different releases..
OracleAS 10gR3 version 10.1.3.X is NOT a full version of the OracleAS.
10.1.3 only includes the following components:
+ Oracle HTTP Server
+ Oracle J2EE Server (OC4J)
+ OPMN Process.
+ SOA/BPEL components