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This topic explains how the Adapter for Supra allows you to describe and report from Supra database views. You should become familiar with these topics, because most of the concepts affect the way Supra files are described to the server.
Each Supra database can be described as a segment in a Master File. You can describe multiple views in a single Master File if the key of one view is a field in the other view. This embedded cross reference is described with the KEYFLD and IXFLD parameters in the Access File.
A Supra database is a collection of one or more views. The Supra Relational Data Manager (RDM) provides access to physical fields from one or more files in a flat, two-dimensional format. A set of field values is a row. A Supra database consists of one or more views, each of which consists of one or more rows. You can define a subset of rows or reorder the columns according to your needs. This subset of data is called a user view. A column is the smallest logical unit of data a program or user can request.
After creating the view, the database administrator (DBA) defines it in the directory. The DBA can also designate one or more columns as keys to the view. The keys can be used to locate a specific set of rows.
In summary, the terms essential for understanding the data model are as follows:
Term |
Definition |
---|---|
View |
Set of one or more rows as defined by the Database Administrator (DBA). |
User view |
Subset of a view which may consist of all or part of the view. |
Row |
Set of one or more related data items stored in computer memory. |
Column |
In a row, a specified area used for a particular category of data. |
Value |
Quantity assigned to a constant, variable, parameter, or symbol. |
Key |
One or more data items, the contents of which identify the type or location of a row or the ordering of data. |
Keys can appear anywhere in the view. The DBA can define different types of keys:
You can access a set of rows by assigning values to the keys of the view (if there are any). The DBA determines which columns are keys and defines them on the directory. You can use the keys to locate a specific record or to perform a generic read. You can also access a set of rows sequentially by not supplying any values for the keys.
To map a Supra structure to the server you must set up two files, the Master File and the Access File.
Supra concepts correspond to the following Master File elements:
The Master File should include only needed columns from the Supra view. Performance may be improved if you do not specify all the columns defined in the view. Even though it is possible to define the columns in an arbitrary order, rearranging key columns may adversely affect performance.
The Access File contains Supra DBMS specific information.
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