IBM i Data Physical Files Support

UDM for IBM i supports data physical files with a CCSID and with no DDS (default CCSID of 65535).

If a DDS is attached to a data physical file on the source side, that same DDS is used when doing an IBM i to IBM i copy on the destination side unless the DDSFILE, DDSLIB, and/or DDSMBR attributes are overridden on the destination side to indicate a different DDS or no DDS is to be used.

The DDS itself is not copied, so it must reside on the destination side.

There is one exception: if the source side is a file created via FTP, the created file has an associated DDS file. The associated DDS specifies a single field and DDS source identified by the file is deleted following completion of the job under which the file was created. When UDM identifies a file created by FTP, it ignores the DDS and copies the file as though no DDS exists.

When copying any file to a destination data physical file with the DDSFILE, DDSLIB, and DDSMBR attributes set to point to the file, library, and member of an existing DDS, that DDS is attached to the destination file.

In either case, whether from the source or explicitly on the destination side, if a DDS is used on the destination side, the resulting file's CCSID is determined by the DDS or by the job CCSID settings if not provided by the DDS.

If the source file has no DDS, or if the destination attributes specify no DDS (or are overridden to do so to prevent the source attributes used in an IBM i to IBM i copy), the destination data physical file is created with a CCSID of 65535 (meaning no translation).

UDM will issue an informational message if you try to transfer a source file that has a DDS in text mode that tells the user corruption is likely. This is because text translation on the field level is governed by the DDS. UDM does not support independent field-level text translation.

Caution about Text Mode Transfer of Files with DDS

In general, files with DDS should be transferred using binary mode only.

There are instances when a user may want to use text mode. However, without an advanced user's thorough understanding of CCSID and code page, unexpected results will occur.

As of Universal Products for IBM i release 3.2.0, when the correct conditions are met, UDM maps the code page attribute associated with the data stream to a CCSID. This occurs only when data is transferred to a data physical file in text mode with an associated DDS file.

This mapping is used on the LIB file open to obtain translation between the data stream and data in fields with CCSIDs other than 65535. The translation is done by IBM i; UDM is in no way involved with this translation process.