Air carrier flight crew reported receiving a RA while on an arrival procedure.

Attributes
ACN	1515926
Time
Date	201802
Local Time Of Day	0601-1200
Place
Locale Reference	ONT.Airport
State Reference	CA
Aircraft 1
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR SCBBY2
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	Climb
Flight Plan	None
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument
Events
Anomaly	ATC Issue All Types Conflict NMAC
Miss Distance	Horizontal 0 Vertical 400

Narrative:

Level at cruise altitude of 240. Directed to descend to FL220. Once in contact with la approach cleared to descend via the Scooby2 which has a bottom altitude of 4300 ft. After several altitude interventions by ATC we were finally cleared to descend via the Scooby2 out of 14000 ft. At 11000 ft a target appeared on our navigation display climbing at high rate in a direct vector to a collision. Out of 9000 ft a TCAS alert sounded with 'climb'. We climbed rapidly and when we received the all clear statement we cleared the traffic by 400 ft. Now high on the arrival for Scooby2 runway 26R due to the TCAS RA; informed ontario appr of the RA. Landed with no further issues. Controllers over-saturated. Do not have enough knowledge on ATC to offer any suggestions.

Original NASA ASRS Text

Title: Air carrier flight crew reported receiving a RA while on an arrival procedure.

Narrative: Level at cruise altitude of 240. Directed to descend to FL220. Once in contact with LA Approach cleared to descend via the Scooby2 which has a bottom altitude of 4300 ft. After several altitude interventions by ATC we were finally cleared to descend via the Scooby2 out of 14000 ft. At 11000 ft a target appeared on our Navigation Display climbing at high rate in a direct vector to a collision. Out of 9000 ft a TCAS alert sounded with 'Climb'. We climbed rapidly and when we received the all clear statement we cleared the traffic by 400 ft. Now high on the arrival for Scooby2 Runway 26R due to the TCAS RA; informed Ontario Appr of the RA. Landed with no further issues. Controllers over-saturated. Do not have enough knowledge on ATC to offer any suggestions.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.