Attach and Detach External Reference

If you attach a drawing as a XREF , the referenced drawing is linked to the current drawing. Any changes to the xref drawing are displayed in the current drawing when it is opened or reloaded. You can also insert an entire drawing as block in current drawing, but the block is not associate with the original drawing.

When you attach an external reference, its elements like layers (XREF), linetypes (LINETYPE), text styles and other elements are not added to the current drawing, but also linked from the referenced file.

When you detach one or more DWG references from your drawing, all instances of a specified xref are erased and the xref definition is marked for deletion in the definition table. Only xrefs attached or overlaid directly in the current drawing can be detached; nested xrefs cannot be detached.

You can not delete the related layer definition by deleting the xrefs. Using Detach option removes the xrefs and all associated information.