To generate an ARCHDEF file, select your project in the Eclipse Navigator, right click and select Team -> Generate Archdef.
From a project mapped to SCLM in your workspace, you can invoke Generate Archdef function to generate an Archdef file for the project in your workspace based on the members in the selected project and additional information specified in the dialog.
Using the Archdef Name dialog, you can specify other members to be included in the Archdef which are in SCLM, but not in the selected project. The action creates ARCHDEF with the specified name in the root of the selected project.