Why oozie run configuration in xml will replace local configuration?

[Mshinom]

Now I will call the jobRun method with some special parameters to run coordinator job. And these parameters were writed in co_XXX.xml. I want these special parameters not to be replaced with those in co_XXX.xml. Can I do these modifies?
Modifies:
core/src/main/java/org/apache/oozie/command/coord/CoordActionStartXCommand.java:
143:--XConfiguration.copyNotReplace(localConf, runConf);
143:++XConfiguration.copyNotReplace(localConf, runConf);
core/src/main/java/org/apache/oozie/util/XConfiguration.java:
++ public static void copyNotReplace(Configuration source, Configuration target) {
++ for (Map.Entry<String, String> entry : source) {
++ if(target.get(entry.getKey()) == null) {
++ target.set(entry.getKey(), entry.getValue());
++ }
++ }
++ }
My purpose is that let the run configuration not replaced by configuration in xml.
What extra erros will happen if I do these changes?
And I want to know original purpose of original replacing.
Thanks very much for any suggestions!