Progress/400
Product Guide
Joined Logical Files and Progress Queries
DB2/400 supports the joining of logical files. Progress/400 supports these joined files as virtual files. The Progress/400 Data Dictionary has read-only access to these virtual files, so you cannot change or otherwise manage them as you change or manage normal files from the Progress/400 Data Dictionary. See the OS/400 documentation for information on creating joined logical files.
Queries against a joined logical file have certain limitations. Progress uses RECIDs to manage records and improve performance on queries, but RECIDs have little meaning on the AS/400. As a result, queries against joined logical files can return unpredictable results, and some query types might not return the correct set of records.
For example, the following queries work correctly against joined logical files:
Because the following query contains a nonkeyed field name, it returns unpredictable results when used against joined logical files:
Other queries might or might not work properly. Before you include a query against a joined logical file in an application, make sure to determine whether it works in your environment.
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