DB2 guides for certification

--> redbooks from ibm by IBM
-->DB2 9 for z/OS Database Administration: Certification Study Guide by Susan Lawson and
Daniel Luksetich
-->Certification Exam Study Guide by Roger Sanders
-->DB2 Universal Database V8 Application Development Guide
-->DB2 9 New Features by Paul Zikopoulos et al
-->Beginning DB2: From Novice to Professional by Grant Allen
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if you have any suggestion kindly let others know ..........

which is better mainframe or DBA?

can any body suggest me which is better course in software
is it IBM mainframe or DBA??