Commercial banks reversed course in the final three months of 2004 and significantly increased their holdings of mortgage-related securities, according to a new Inside MBS & ABS analysis of bank call report data. The commercial banking sector reported a record $876.4 billion of mortgage securities on its books at the end of last year, a 13 percent increase over year-before levels. But bank MBS holdings had been declining through the middle of 2004 after reaching…