AutoCAD 2008 User's
Guide > Share Data Between
Drawings and Applications > Reference Other
Drawing Files > Resolve Referenced
Drawing Errors >
Resolve Circular External References
If a referenced drawing contains a sequence of nested references that refers back to itself, an error message is displayed.
A reference file that contains a sequence of nested references that refers back to itself is considered a circular reference. For example, if drawing A attaches drawing B, which attaches drawing C, which attaches drawing A, the reference sequence A>B>C>A is a circular reference.
If the program detects a circular reference while attaching an xref, a warning is displayed asking you if you want to continue. If you respond with yes, the program reads in the xref and any nested xrefs to the point where it detects the circularity. If you respond with no, the process is halted and the xref is not attached.
If a circular reference is encountered while loading a drawing, an error message is displayed and the circular reference for the current session is broken. For example, if you have the circular reference A>B>C>A, and you open a.dwg, the program detects and breaks the circularity between c.dwg and a.dwg. The following error message is displayed:
Breaking circular reference from C to current drawing.
