Does anyone have any method for changing datasources/models/packages from classic query mode (thus using 32-bit database client) to DQM (thus using 64-bit clients) in Cognos 10.1.1 in place?
Or once cqm/dqm is set, is it non-modifyable?
You can certainly change it. Here's an article on getting started, as there are a few places you need to set this (connection, FM package)
http://www.ibm.com/support/knowledgecenter/SSMR4U_10.2.1/com.ibm.swg.ba.cognos.dyn_query.10.2.1.doc/c_dqm_dyn_query_setup.html