Implementing database design
After you design your databases and application programs you must describe their characteristics to IMS™ before you can use them.
You must describe the physical and logical characteristics of your databases to IMS by coding and generating a database descriptor (DBD) for each database.
Before an application program can use the database, you must tell IMS the application program's characteristics and use of data and terminals. You tell IMS the application program characteristics by coding and generating a program specification block (PSB).
Finally, before an application program can be scheduled for execution, IMS needs the PSB and DBD information for the application program available in
a special internal format that is called an application control block (ACB). The
following diagram depicts how the information is gathered from a PSB and DBD.
Figure 1. Distributed and z/OS® environments