If a referenced drawing cannot be located when you open a drawing, an error message is displayed. There are several options available to you if this occurs.
The program stores the path of the drawing that is used to create the referenced drawing. Each time you load or plot the drawing or use the xref Reload option in the External References palette to update the xref, the program checks this path to determine the name and location of the referenced drawing file. If the name or location of the drawing file has changed, the program cannot reload the xref.
If the program cannot load an xref when it is loading your drawing, it displays an error message. In this example, the program can't find the xref HOUSE:
"\acad\dwg\house.dwg": Can't open file
** Error resolving Xref HOUSE.
For each insertion of the referenced drawing, the program displays text (at the location, scale, and rotation angle of the original reference) that contains the path of the missing xref. You can use the XREF Path option to update or correct the path.
One way to avoid these errors is to be sure that when you give other people files that have xrefs attached, you also give them all the referenced files.
When the drawing is reopened and the nested xref is loaded, the program attempts to find the xref in the original xref path first. If the xref is not found, the following search is initiated in the order shown:
This ensures that revisions made to the xref are reflected in the current drawing and also makes it possible for the xref to be found if its path has changed.
For example, suppose that the xref tree of the current drawing A is A>B>C, and the owner of drawing B changes the path of xref C to point to C1.dwg. When drawing A is reopened, it reflects the path change in drawing B and displays C1.dwg. However, if C1.dwg is not found, the program looks for xref C at the last location it was saved in drawing A.