iRule Persistence vs Primary persistence

Hi,

I am validating a configuration of exchange based on iApp and I see that in VS_https is configured default persistence profile (insert cookie) and Fallback persistence (source address), but additionally see that there are an irule "combined_persist_irule7" and this has several methods based persistence service exchange as ActiveSync, ECP, OAB, Anywhere, etc. I would like to know if irule persistence takes precedence or default and fallback persistance.