Exhibit A

JOINT FILING UNDERTAKING

The undersigned parties hereby agree that the Schedule 13D filed herewith (and any amendments thereto) relating to the Common Stock of Acxiom Corporation is being filed jointly on behalf of each of them with the Securities and Exchange Commission pursuant to Section 13(d) of the Securities Exchange Act of 1934, as amended.

		ValueAct Capital Master Fund L.P., by
		VA Partners, LLC, its General Partner
	By:	/s/ George F. Hamel, Jr.
Dated: August 7, 2006		George F. Hamel, Jr., Managing Member
		VA Partners, LLC
	By:	/s/ George F. Hamel, Jr.
Dated: August 7, 2006		George F. Hamel, Jr., Managing Member
		ValueAct Capital Management L.P., by
		ValueAct Capital Management, LLC, its General
		Partner
	By:	/s/ George F. Hamel, Jr.
Dated: August 7, 2006		George F. Hamel, Jr., Managing Member
		ValueAct Capital Management, LLC
	By:	/s/ George F. Hamel, Jr.
Dated: August 7, 2006		George F. Hamel, Jr., Managing Member
	By:	*
Dated: August 7, 2006		Jeffrey W. Ubben, Managing Member
	By:	/s/ George F. Hamel, Jr.
Dated: August 7, 2006		George F. Hamel, Jr., Managing Member
	By:	*
Dated: August 7, 2006		Peter H. Kamin, Managing Member
	By:	*
Dated: August 7, 2006		Louis J. Andreozzi
	By:	*
Dated: August 7, 2006		J. Michael Lawrie

*By:	/s/ George F. Hamel, Jr.
	George F. Hamel, Jr.
	Attorney-in-Fact