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) […]
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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 […]
IMS DB – Secondary Indexing Secondary Indexing is used when we want to access a database without using the complete concatenated key or when we do not want to use the sequence primary fields. Index Pointer Segment DL/I stores the pointer to segments of the indexed database in a separate database. Index pointer segment is […]