Date: 201712
Local time of day: 1801-2400
Location: ZLA.ARTCC, CA
Flight conditions: VMC
Weather elements / visibility: Turbulence
Light: Daylight
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent; Initial Approach
Airspace: Class A ZLA
ATC / advisory: Center ZLA
Aircraft component: FMS/FMC
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Workload
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance; Flight Crew FLC Overrode Automation
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I was the Captain and non-flying pilot during a descent on the HLYWD 1 Arrival into LAX. Conditions were moderate chop; VFR. Flight attendants were pre-seated due to the expected deteriorating rides into the LA Basin. (Strong North winds at 90+ Santa Anna event)We had been cleared to descend via the arrival. The bottom altitude was set at 12;000 in accordance with the procedure. Both flight crew members had previously verified the arrival prior to beginning the HLYWD 1.At the time of the event the #2 (left) autopilot was on; with the aircraft in a 1000FPM descent; below the path; with it expected to capture the path from below. The next restriction was between 30;000 and 24;000 at BRUEN. Speed was assigned at 300 KTS by ATC with a request to inform if we needed to slow due to the moderate chop.Left (Captains) FMC failed with the following messages displayed along with a Master warning.1) 'FMC Fail'2) 'Offside FMC Control' on FMC3) 'AP' 1 fail4) 'CAT 3' fail5) 'FM' light on CA FMCIn addition numerous repeating individual Master Caution chimes were heard. The First Officer (FO) continued to fly the aircraft. We verified that this was not an Immediate Action or Electronic Centralized Aircraft Monitor (ECAM) exception; for each item; in priority order. No ECAM procedure was displayed. We verified that the Aircraft was on Autopilot 2 and then consulted the [Company] QRH. The QRH explains that a manual computer reset could be initiated if the 'Auto reboot' is not successful. Due to the high workload I decided to not attempt a manual reset (I would have been required to leave my seat and cycle Circuit Breakers (CB). The Captain's Moving Map and Constraints were gone with nothing displayed on my PFD (with the exception of error messages). At this time the FO had a moving map with no displayed constraints. (We would later learn this was due to the dumping of all arrival data during the second auto reset)The Left FMC continued attempting to reset the Right FMC. On the second auto attempt a message 'Set Offside Ring Mode' appeared. FO's FMC went blank and all FMC data on left FMC was lost. The Autopilot disengaged. The FO reinstalled the arrival into the left FMC and then reengaged the Autopilot. (Captain's FMC was inoperative at this time; requiring cross cockpit data entry).  The aircraft was in a 1000 FPM descent; and we descended 2200 feet below the BRUEN fix floor of 24;000 feet. (At this time no VNAV constraints were displayed on either PFD) ATC asked us to stop our descent at 22;000. We complied and continued to evaluate Aircraft systems and re-validate the approach data. At that time we became aware that the VNAV was disengaged and the deviation below slope was displayed on the Performance page. We deselected VNAV and then reselected VNAV. The Path was re-displayed as above the aircraft. At this time we determined that the aircraft was 2000 feet below the fix that was ahead of us. ATC contacted us about an altitude deviation and I asked them to standby as were evaluating an aircraft systems failure. We became aware of our position when the map and constraints were finally redisplayed on the FO's PFD. No Nav fixes/or Constraints were ever displayed on the CA PFD after the initial failure.After completing the QRH procedures; we contacted ATC. We complied with the read back and informed them that were partial single FMC and unable to continue at this time with the HLYWD1 Arrival. We were issued a heading; altitude and speed. After all check lists were completed; aircraft status verified; and the HLYWD 1 Arrival re-verified; we informed ATC that we could return to the HLYWD 1 in a degraded single FMC configuration.Shortly after being cleared to descend via the Arrival the right FMC failed again due to the third Auto reset.My FMC displayed OFFSIDE Ring Mode and my FMC went blank with the display dead and dark.We were VMC with all terrain clearly visible. The aircraft was at 22;000 feet and we were above the path.My PFD displayed 'No MAP Constraints'; 'Flap Not Avail'; 'Terrain Ring' all with associated Master warnings and Caution chimes. I became task saturated after resetting the FO's FMC multiple times and asked that we be cleared for the ILS 25L. We were cleared to slow to 240 knots and cleared for the approach ILS 25L. We slowed and descended to the glide slope path. The FO armed the approach mode and captured the glideslope. This was the first time we had positive path or slope guidance since the first FMC failure. The aircraft was high up to the FAF at LIMMA. We were fully configured by 1500 feet and stable at 1000 feet.My glideslope was not displayed as Left FMC ILS tuning was not available. I backed the ILS descent of the Standby until the VASI came into view. (I could have 'Manually' tuned my ILS) but it was not a priority. The comparator gave me an 'ILS disagree message' at 1000 feet. We landed without incident.


Second narrative: [Report narrative contained no additional information.]


Synopsis: A321 flight crew reported a failure of the FMC during approach; causing altitude restrictions on the arrival to be missed.