A reference attachment that specifies the DGN file containing the attached model by its full (absolute) path is not portable across directories, WorkSets, and networked systems. Administrators can prevent the storage of full paths in attachment data by setting the configuration variable MS_DISALLOWFULLREFPATH. You can take these additional measures to make sure that your reference attachments are portable:

• If you do not expect the internal directory structure of your WorkSet to change, the best way to ensure portability when attaching references is to turn on Save Relative Path in the Attach Reference dialog. This causes the relative paths to DGN files that contain attached models to be saved as attachment data in the open DGN file.
• Where you are sure that the internal directory structure of your WorkSet will not change, you can set the configuration variable MS_ALWAYSRELATIVEREFPATH. When this configuration variable is set, MicroStation always turns on the Save Relative Path check box and disables it so that it cannot be turned off.
• If the WorkSet directory structure is in flux, or if DGN files are shared between WorkSets, using relative paths would not give you sufficient flexibility to ensure the portability of your reference attachments. In these situations, you should define the configuration variable MS_RFDIR or a custom configuration variable to specify the directory in which references reside, and attach references using this configuration variable. The configuration variable name, but not its definition, is saved as attachment data. If the WorkSet files are then moved, for example, to another directory or a file server, the only change needed is to redefine the variable. Defining multiple custom configuration variables, such as WorkSet-specific or data type-specific variables, provides even greater flexibility.