Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 9
Communication Breakdown; Confusion; Situational Awareness
Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action
Aircraft; Airspace Structure; Human Factors; Procedure
While working Sector 21 during a busy departure/arrival push; Aircraft X reported that on the previous sector he had an RA and had to descend for the traffic.  The traffic was in my airspace; but SoCal Tracon was working the aircraft climbing into my airspace as LOA dictates.  This is problematic because often enough they do not issue or look for VFR traffic in our sky even though they are climbing into it.  This is what happened with Aircraft X.  We don't really know when they climb or turn aircraft and is often too late to call them with traffic.  I did see the traffic at 15;500 feet and did issue it to some of my aircraft; but was too busy to tell if it would have been a factor for Aircraft X who was talking to SoCal and apparently did not see the traffic (or did and didn't do anything to avoid it).Either give SoCal TRACON more airspace to climb aircraft in their own sky or change the LOA to only climb to the top of their airspace (13;000 feet).  This had been a problem for as long as I have been assigned to ZLA.
ZLA Controller reports of pilot telling him about a RA that he had while talking to the underlying Approach Control.  Controller alluded to this happening all the time.