The FRED series Total Credit Market Assets Held is now known as All Sectors; Credit Market Instruments; Asset.
The source series id is FL894104005.Q.
This series appears in Table L.1. For further information see the assistance provided in the guide to the Financial Accounts at http://www.federalreserve.gov/apps/fof/.
Board of Governors of the Federal Reserve System (US), All Sectors; Credit Market Instruments; Asset, Level [TCMAH], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/TCMAH/, August 30, 2015.