External References and Data Management
What you must understand
XREFs, their attachment paths, and how they resolve are core. Know ATTACH versus OVERLAY (overlay avoids circular nesting), relative versus absolute paths, and the Reference Manager or XREF palette for repathing. Understand binding (Bind versus Insert) and how bound xrefs convert to blocks. Know raster images, PDF underlays, and DWF underlays as reference types. Data management includes layer states, purge, audit, recover, and the difference between PURGE and -PURGE. Also know how to detach, unload, and reload references.
Traps that appear in questions
- Detach removes the reference entirely; unload keeps the definition but hides it; reload refreshes a changed file.
- Bind Insert merges named items with prefixing behavior differing from Bind.
- Overlay xrefs do not appear in host drawings that attach the current drawing, preventing circular references.
- Purge will not remove items in use, nested items, or some named objects until dependencies clear.
- Missing xrefs show as unresolved; repathing fixes them without reattaching.
Worked example
A drawing references a base file that has moved. Open the XREF palette, select the reference, choose Change Path, and browse to the new location. Use relative path so the reference survives if the project folder is copied. If the reference is no longer needed, choose Detach rather than Unload to remove it cleanly.
Rule of thumb
Ask whether the goal is to remove, hide, or refresh: detach, unload, or reload respectively. Choosing the wrong verb is the most common trap.