Using DDL to define databases and program views

In IMS systems that are enabled to manage application control blocks (ACBs), you can define databases and program views by using standard SQL data definition language (DDL) statements.

Using DDL statements, you can describe the physical and logical characteristics of databases, as well as the characteristics of the programs that use the databases and how the programs use data and terminals.

To simplify the definition of IMS databases with DDL, IMS provides defaults for many IMS-specific settings. The default values conform to common best practices in IMS database design.

When you submit DDL statements, IMS creates the ACBs automatically and stores the database (DBD) and program view (PSB) definitions in the IMS catalog. You do not use generation utilities.

Depending on the DDL specifications and the specifications in the IMS system, IMS can automatically activate the database and program view definitions in the IMS system. When DDL changes are not activated automatically, the definitions are stored in the staging data set of the IMS catalog and you activate them by issuing the IMPORT DEFN SOURCE(CATALOG) command. You do not use the online change process to activate the changes.

In IMS systems that support DDL, the IMS catalog is the single, trusted repository for all of your database definitions and the IMS catalog determines which definitions are active in the IMS system. The online IMS system does not use PSB, DBD, or ACB libraries. If you have tools or procedures that require these libraries, you can create them from the definitions in the IMS catalog by using the IMS Catalog Library Builder utility (DFS3LU00).