[Serusers] proxy don't query the location table?

Hi, I put the proxy and registar at the two machine. when proxy deal with calling, I found that proxy don't query the callee information from the database. I sniffed the data traffic with ethereal. the Ser log said in the registrar/lookup.c lines 81 that: "lookup(): '8644' Not found in usrloc". What I want to know when the proxy and registrar are located on the different devices. how can the registrar tell the proxy the new registered sip ua if the proxy didn't look the callee in the location table. If I am not wrong, the usrloc function get_urecord() did not query the table for every coming call. It attempts to find callee in a hash table. Can that guarantee to find the newest information in the database??? Thanks for your instructions. Best Regards. Zongjun