Introduction to Data Management

Glossary
Glossary-10 15873 Tandem Computers Incorporated
Protection view. In NonStop SQL, a view derived from a single table by taking either a
projection of the columns of the table, a selection of the rows in the table, or both. A
protection view provides a form of field level security because the view can be
secured, updated, and read.
PS TEXT EDIT. See TEDIT.
Query. Generally, a request for data from the database. In NonStop SQL, the
execution of a SELECT statement against a table or view.
Query optimization. The selection by the NonStop SQL compiler of the best access path,
join order, type of join, sort strategy, and so forth for a data manipulation statement.
RDF. The Remote Duplicate Database Facility, a utility that furnishes database backup
by duplicating transactions that occur on one database to an identical copy of that
database on another system.
RDFCOM. A utility program that allows you to configure, initialize, monitor, start, and
stop RDF.
RDFSCAN. A utility program that allows you to quickly scan an RDF log file.
Recompilation. See Automatic recompilation.
Record. The basic unit of storage in a file or database, pertaining to a particular item.
For instance, a customer's bank account record contains information about that
particular customer's account. A record is the smallest logical unit of data that can be
read from or written to a file; in a relational table, a record is represented as a row.
Relational database. A database in which data is represented as a collection of relational
tables containing rows and columns.
Relational database management system. A database management system that organizes
records in a tabular format. Each file contains only one kind of record--for instance,
checking account records only or bank employee records only. Thus, all records in a
particular file have the same structure and field arrangements, allowing users to view
the file as a table where each row is a record and each column is a collection of values.
Relational table. A table in a relational database.
Relative file. A file in which each new record is stored at the relative record location
specified by its primary key, and whose primary key is either a user-defined or
system-defined relative record number that indicates the record location. Each record
location can be regarded as a numbered slot that holds one fixed-length record, with
the primary key identifying the slot number. Records can be updated or deleted, but
not lengthened or shortened.
Relative table. A table stored as a relative file. Columns can be added, provided the
record length is large enough to include the added columns.
Remote Duplicate Database Facility. See RDF.