The CE-APM userID (as defined in the wily-Introscope properties file's SYSVDB2.username parameter) did not have an associated password in its RACF definition.
By redefining the CE-APM userID (as stated in the wily-introscope properties file's SYSVDB2.username parameter) to RACF with a password, the communication between CE-APM and XNET/SYSVIEW for DB2 proved successful. DB2 metrics could now be viewed in the UI.
You could also define the CE-APM userID to RACF with the 'NOPASSWORD' parameter. In ACF2 it is the 'RESTRICT' parameter that can be used for an ID that does not have an associated password.