Hi Jack,
I am listing down the probable options below.
1. Please review your JDK Version and update to the most recent versions with compatibility to your platform.
2. Since you have mentioned that yours having Oracle Database then please consult the below note.
739829 - Central Note for Performance of EP KMC
3. You can also follow the below note for recommended JVM settings.
723909 - Java VM settings for J2EE 6.40/7.0
4. Sometimes the reason may also be the Garbage Collector. For that you can also refer the below links.
Avoid Performance Bottlenecks from Java Garbage Collection
Demystifying Java-Based Load Tests and Their Results
5. As a overall performance tuning for EP 7.0 you can also refer the below links as well.
Performance Best Practices Guide for SAP NetWeaver Portal 7.0
.Hopefully you will some useful information from the above links.
Thanks and Regards
Anurag