Cataloging Data Sets
A dataset may or may not be cataloged
If it is cataloged, then it can be referenced by its data set name, and it is not necessary to provide a volume name or other technical information about that data set.
To determine what catalog a particular data set is in, MVS uses the data set name’s highest level qualifier.
INSGSH1.JUNK.TRASH.STUFF would be cataloged in the INSGSH1 catalog.
(Much more about this in the JCL part of the course.)