When you issue a FOCUS retrieval request, the adapter translates it into an equivalent set of IMS DL/I (Data Language/I) calls. When the IMS DBMS returns data in response to the request, the adapter passes this data to the FOCUS Report Writer for formatting and, possibly, additional processing. The Report Writer can process data from any FOCUS-readable data source. The adapter does not recreate the data in the form of a FOCUS database.
The following diagram depicts report processing:
FOCUS and the IMS DBMS interact as follows:
The adapter creates SSAs (Segment Search Arguments) to optimize DL/I calls based on request criteria and thus performs two primary tasks:
Just as important, the adapter initiates and monitors communication between itself and the IMS DBMS and provides descriptive error messages when necessary.
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