Glossary D
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DBTT extent
see DBTT
DBTT page
Page containing the DBTT or part of the DBTT for a particular record type.
DCAM
Component of the TRANSDATA data communication program.
DCAM application
Communication application using the DCAM communication method. A DCAM
application enables communication between
– a DCAM application and terminals.
– different DCAM applications within the same or different hosts, and with
remote configurations.
– a DCAM and a openUTM application.
DDL
(Data Description Language) Formalized language for defining the logical data
structure.
deadlock
Mutual blocking of transactions.
A deadlock can occur in the following situations:
– Data deadlock: This occurs when transactions block each other with
contending access.
– Task deadlock: This occurs when a transaction that is holding a lock cannot
release it, since no openUTM task is free. This deadlock situation can only
occur with UDS/SQL-openUTM interoperation.
descending key (DESC key)
Primary key of a set. Determines the sequence of member records in the set occur-
rences to reflect descending key values.
direct access
Access to a record via an item content. UDS/SQL supports direct access via the
database key, hash routines and multi-level tables.
direct hash area
See hash area.
distributed database
A logically connected set of data resources that is distributed over more than
one UDS/SQL configuration.