Execute Direct Access Program: Difference between revisions

Revision as of 22:35, 8 May 2011

Revision as of 22:39, 8 May 2011

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Existing records may be read or updated. The dataset may not be created nor extended using XDAP; for that purpose BSAM or BPAM is required. XDAP may coexist with BSAM or BPAM, and several OS components are implemented in this way.

The programmer is responsible for computing the full direct access record identifier, MBBCCHHR. System algorithms are available for calculating the MBBRRHHR from a TTRN. AdditionalSystem systemdata, algorithmsin the form of "track capacity tables", are available for calculating the TTRN from a record number.

List and Execute forms of XDAP are supported, whereby a prototype form, called the List Form, is expanded as data, and a functional form, called the Execute Form, is expanded as instructions. XDAP is also supported in a conventional form, in which case the two forms are combined, and is expanded as inline data and instructions.