IMS DB – DL/I Terminology Hierarchical databases work on the relationships between two or more segments. The following example shows how segments are related to each other in the IMS database structure. Root Segment Points to note − The segment that lies at the top of the hierarchy is called the root segment. The root […]
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IMS DB – Control Blocks IMS Control Blocks define the structure of the IMS database and a program”s access to them. The following diagram shows the structure of IMS control blocks. DL/I uses the following three types of Control Blocks − Database Descriptor (DBD) Program Specification Block (PSB) Access Control Block (ACB) Database Descriptor (DBD) […]
IMS DB – Programming An application program which includes DL/I calls cannot execute directly. Instead, a JCL is required to trigger the IMS DL/I batch module. The batch initialization module in IMS is DFSRRC00. The application program and the DL/I module execute together. The following diagram shows the structure of an application program which includes DL/I calls […]