Relationship Between Libraires, Files and Members

On the AS/400 every file is in a library. The data in the file is actually stored in individual members. Typically, a file has only one member and it has the same name as the file.

When you use commands to work with files, there is a parameter that gives you the ability to choose which member to use. The default for this parameter is *FIRST. So you rarely actually specify the member name.

So, the data is in a member which is in a file which is in a library.

Imagine a sheet of paper with a spreadsheet printed on it. The lines on the spreadsheet are like the records. If you put only one sheet of paper in a file folder and you put that folder in a cabinet, if would be similar to the AS/400 file structure:

        Cabinet    ----->    Library
        File Folder ----->    File (or database file)
        Sheet of Paper ----->    Member of the file
        Data on the Sheet ----->    Records in the Member  
If you want to see the data in a file, you are actually wanting to see the data in the first and only member of the file. This is why the command to display the data in a file is not DSPF or DSPFIL.

The command to display the data in a member of a file is:

DSPPFM - Display Physical File Member

The term physical file refers to the records in the member that are in arrival sequence. With the database facility, you can build logical views (indexes) to select only certain fields and only certain records and to resequence the records.

However, there is no Display Logical File Member command. You usually simply view the data using DSPPFM and use your imagination to picture the logical data. In a while, there will be a tip for seeing the logical file data.

Back to Basic AS/400 Tips    |    Back to Main Page    |   Contact Info