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System Control Blocks

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DATA EXTENT BLOCK -- ORDINARY<br />

The data extent block (DEB) contains an<br />

extension of information in the DCB. Each<br />

DEB is associated with a DCB, and the two<br />

point to each other. The DEB contains<br />

information concerning the physical<br />

characteristics of the data set and other<br />

information that is used by the control<br />

program. Figure 12 illustrates the format<br />

of the DEB. Descriptions of the fields<br />

follow the illustrations.<br />

This data extent block is used in all<br />

access methods and is used in QTAM by a<br />

message control program to describe a queue<br />

which is on a direct access storage device<br />

or to describe a line group. (QTAM<br />

processing programs use a DEB described<br />

separately.)<br />

DEB 113

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