Overriding only one dataset in 3 concatenated datasets

Mention the override step with specific DD names with spaces for which we are not going to specify with any overrides from JCL.

For eg:

//STEP1.PRC   DD DSN=
//DDF1              DD DSN=MLOGI.DATA.FILE2,DISP=SHR
//DDF2              DD DSN=

Do not specify DD names with DUMMY as the datasets will be considered as DUMMY.

For eg:

//STEP1.PRC   DD DUMMY
//DDF1              DD DSN=MLOGI.DATA.FILE2,DISP=SHR
//DDF2              DD DUMMY