Types of data sets

We mentioned in Using ISPF/PDF that a data set contains information that can be stored and retrieved. Data sets can contain many kinds of information – programs, numerical data, inventory records, memos, reports, and so on.

TSO/E manages data sets much the same way you might manage a filing system. When you first begin a filing system, you might have only a few categories; for instance, bills, insurance, and taxes. You delegate a file to each category, mark an empty file folder with the category name, and begin to put appropriate information in each file.

Similarly, TSO/E manages simple files called sequential data sets. These files can have one or more names separated by periods such as BILLS, or CURRENT.BILLS, or MY.CURRENT.BILLS. The contents of sequential data sets are arranged in sequence in a single file.

00001  1/04   Groceries            $42.21       Paid
00002  1/05   Gasoline             $18.00       Paid
00003  1/13   Towing charge        $25.00       Unpaid
00004  1/14   Snow tires           $70.95       Unpaid
00005  1/16   Groceries            $67.14       Paid
00006  1/16   Gas and electric    $112.52       Unpaid
00007  1/17   Telephone            $80.05       Unpaid

When your file for bills becomes so full it is difficult to find information in the file, you can subdivide the information into smaller categories. Suppose you decide to divide the file into the categories ‘paid’ and ‘unpaid’. You then mark up two new folders with the new category names. Both folders are still under the general category ‘bills’.

Similarly TSO/E manages subdivided files called partitioned data sets or PDS. A PDS can contain one or more members. Each member is like a sequential data set in that the contents are arranged in sequence. Partitioned data sets generally have three names separated by periods and a member name in parentheses.

MY.CURRENT.BILLS(PAID)
MY.CURRENT.BILLS(UNPAID)

Information you might have in a PDS are programs of a particular type, such as COBOL programs with one program per member.

MY.TEST.COBOL(PROG1)
MY.TEST.COBOL(PROG2)
MY.TEST.COBOL(PROG3)
MY.TEST.COBOL(SAMPLE)