How HD records are stored in multiple data set groups

You specify in the DBD statements which segment types are placed in a data set group. IMS then loads the segments into the correct data set group.

The figure below shows one database record:

• Stored in an HDAM or a PHDAM database using two data set groups
• Stored in a HIDAM or a PHIDAM database using two data set groups

In this example, the user specified that four segment types in the database record were put in the primary data set group (COURSE, INSTR, LOC, STUDENT) and two segment types were put in the secondary data set group (REPORT, GRADE).

In the HDAM or PHDAM database, note that only the primary data set group has a root addressable area. The secondary data set group is additional overflow storage.

Figure 1. HD database record in storage when multiple data set groups are used