Progress/400
Product Guide
Virtual Tables
The DataServer can access both physical and logical files on the AS/400. Physical files are analogous to Progress tables and logical files are analogous to Progress indexes. The AS/400 supports three distinct types of logical files in addition to those that support standard indexes:
To support these types of logical files, the DataServer places limitations on how and where you can use them. A logical file is classified as a Progress/400 virtual table if it is a join, if its record format is different from the physical file on which it is based, or if it contains more than one record format.
In the case of multiple record logical files, the DataServer treats each record format as a separate table. For example, the logical file ORDERLIN has two record formats identified as ORDER and ORDER_LIN. The DataServer represents this file as two tables in the Progress/400 Data Dictionary-ORDERLIN_ORDERR and ORDERLIN_ORDER_LINR.
You can view virtual tables through the Progress/400 Data Dictionary. You cannot maintain them because the Progress/400 Data Dictionary has read-only access to virtual tables.
Virtual tables do not support record positioning by relative record number. You cannot use RECID to access records in a virtual table. Any use of RECID with virtual tables produces invalid results. The following code example uses RECID with virtual tables and therefore does not return a valid record:
For information on relative record numbers, see your DB2/400 documentation.
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