Troubleshooting using SDI/SDL traces from CUCM is a pain, in part because the tool within RTMT for doing this is pretty lame. Cisco do make the Voice Log Translator, which tidies up the presentation of traces & provides explanations of many of the fields, very useful! Unfortunately it's not been updated since 2010 & when I tried using it with CUCM 9.1 recently it didn't seem to understand many of the traces. Fortunately there are a couple of alternative tools for wrangling with traces, both made by Cisco employees: TranslatorX & Triple Combo.
Also, don't forget to give the tools from Communications Manager Tools Part 1 a go.