Tech tip from Julia Giancola, Sr. Support Engineer for June 6, 2016
There are five distinct types of Dataviews:
Datacom dataviews are related to elements in Datadictionary, and from there to fields and tables, areas, and databases through the $INTERNAL relationships. They cannot be edited in Ideal, only cataloged. In the catalog process, Ideal reads the Dataview entity in Datadictionary, and follows the relationships to obtain all the information needed for run-time access to the database using CBS. This includes key details, so that can be shown in the display to guide the programmer, even though the keys are not used to generate the requests.
The version number of a Datacom dataview is that of the Datadictionary entity.
VSAM dataviews have source in the Ideal VLS library IDDVW, and only an entity definition in Datadictionary. That is not related to any other entity in the Database or File model. VSAM Dataviews are related to the Programs that use them.
The version number in Ideal does not correspond directly to that in Datadictionary. DD version 1(PROD) is reserved as a tracking record, that holds the number of the current production version in its ACCESS-CODE attribute. DD versions 1001 and up, which show as T001 etc. in DDOL, hold their Ideal status in the ACCESS-CODE attribute, and are always TEST status to DD. The versions show in Ideal displays without the leading digit, and the status shown comes from the ACCESS-CODE attribute. Version 1(PROD) does not show in any index display, as it is not an actual dataview.
Modelled Sequential Dataviews are similar to Datacom dataviews, but connect to the File model (Files, Records) instead of the Database model (Tables, Elements).
Unmodelled Sequential Dataviews are similar to VSAM dataviews. The only difference is the lack of a key section.
SQL Dataviews are dynamically created by Ideal when the CATALOG command is used. They only exist as version 1(PROD), and can be created from Datacom or DB2 tables or views. Re-cataloging a SQL dataview replaces the existing one.
CATALOG produces an object on IDDVW that provides definitions of the buffer layout, and access path, to process the associated rows or records. This is in a compiled form that can be merged into any program using it. VSAM and Unmodelled Sequential Dataviews also have a source form on IDDVW, which may be edited in Ideal if it is considered to be TEST status (Ideal's status, not Datadictionary's). Datacom, Modelled Sequential, and SQL dataviews cannot be edited in Ideal, and all changes must be made in the source (Datadictionary or DB2 catalog).