DFS3434W UNABLE TO OPEN DDNAME '`ddname`'

Explanation
 IMS encountered an error trying to
open the data set with ddname. Either the DD statement
does not exist or the operating system has encountered an I/O error
during open processing.

System action
 The command is ignored.

Programmer response
 The data set for ddname was
probably not created. You must create the data set, if it is an I/O
error.