IMS DB DBD- Mainframe

This video is extracted from IMS DB live training (previous batch) and Uploaded video (DBD creation) for your reference and understanding.

In this video, i explained:

• How to create DBD/ IMS Database and Process
• Macros
• DATASET
• SEGM
• ROOT
• FIELD
• NAME
• ACCESS=HISAM
• BYTES
• START
• TYPE
• DBDGEN
• FINISH
• END

Other details:

In IMS systems that use DBD libraries, use the Database Description Generation (DBDGEN) utility to define a database so that it can be used by an application program

This utility might not be used in IMS systems that manage runtime application control blocks by using the catalog.

A database description (DBD) is a DL/I control block containing all of the database information needed by an application program.

You create a database description (DBD) by coding special macro instructions. These macros become the input to the DBDGEN utility.

You can use only one physical DBD to describe each physical database; otherwise, a user abend, such as 0850, 0852, or 0853 occurs. At execution time, DL/I uses the DBD to create a set of internal control blocks.

The DBDGEN utility defines each DBD with the following database information:

• Segment types
• Physical and logical relationships between segment types
• Database organization and access method
• Physical characteristics of the database
• Define the name and data options of selected exit routines
• Metadata that describes the database and the data stored in the database