Hi Thomas, im not a dynatrace representative but "sync" means synchronization, that means you are waiting for a response for something from a 3rd party.
What you are showing is suspension,I have never seen it without a GC involved, try to correlate the purepath time stamp with your Old/Young generation behavior if you are in Java
Thanks for your answer! I missed out to mention that this example is from C#. I corrected this in my first post now. In the documentation of Dynatrace, there is also just mentioned GC as only example for "synchronization" times.