Introduction to Data Management

Glossary
15873 Tandem Computers Incorporated Glossary-1
Access mode. A specification of the kinds of operations (read/write, read-only, or
write-only) that a process can perform against a file, established when the file is
opened.
Active dictionary. A data dictionary that is always consistent with the current state of
the data it defines. NonStop SQL provides an active dictionary, but ENSCRIBE does
not.
Ad hoc query. A one-time request for data from the database.
After-image. A copy or copied portion of a database record that is made by TMF after a
transaction makes changes to that record.
Aggregate operator. In a relational database management system, an operator that lets
you operate collectively on all rows in an entire table. With such operators, you can
sort all rows by selected columns or join two or more tables together.
Alternate key. A data field that provides an alternative access path to the records in a
file. This path differs from the inherent access path (the primary key) defined for the
file. Unlike primary key values, alternate key values need not be unique--and, in fact,
usually are not unique. In an employee data file, for example, an alternate key might
be the employee's department number. Using this key, a program could access the
data records for all employees who work in a particular department.
ANSI. The American National Standards Institute.
Application. A set of programs designed to perform a specified task, usually involving
operations on a database. See also PATHWAY application.
Audit dump. A tape copy of one or more disk files that contain TMF audit trails. You
request these dumps periodically, so that you can save disk space by purging the
audit trails from the disk.
Audit trail. A series of files containing records of all transactions that change data in
audited tables or files.
Audited file. A file that is flagged for auditing by TMF; TMF monitors all transactions
against an audited file in preparation for possible transaction backout, autorollback, or
rollforward recovery. Any transaction on an audited file is recorded in an audit trail.
Audited table. A NonStop SQL table that is flagged for auditing by TMF; TMF
monitors all transactions against an audited table in preparation for possible
transaction backout, autorollback, or rollforward recovery.
Automatic recompilation. A NonStop SQL compilation that the system performs
automatically at run time when an SQL object program needs to be recompiled;
automatic recompilation occurs, for example, when an SQL statement refers to a table
that has changed since the last explicit compilation of the statement.