z/OS:
For z/OS you can click on the Qualifier... button in the IODFs dialog to open the High-Level Qualifier dialog. You can then specify the qualifier which determines the list of IODFs displayed in the IODFs dialog. The qualifier is the string of up to eight characters that precedes the first period in the data set name. Changing the qualifier displays the list of IODFs beginning with that qualifier.
z/VM:
For z/VM this dialog is not applicable. There is no filter to reduce the number of listed IODFs in the IODFs dialog. Instead, all IODFs are displayed that are available on your accessed minidisks as shown in Figure 1.
Figure 1. IODFs
dialog for z/VM