I have a number of design drawings, some Xref'ed into others, and since these designs get xrefed themselves into the production drawing, many of the xrefs are Attached, whereas some are overlays. I normally keep these preet clear as to whicj is which. I was happily working away in my site grading which has the storm drain pipe network drawing xref attached. I realized I needed to see some of the information contained in my Roads drawing in the grading plan. No problem, xref it. Oh, yeah, now I have the storm drain showing twice since that drawing is also xref attached to the road drawing. No problem, it was just for visual use up to that point, so I deleted the attached xref from the grading drawing. Now the Pipe drawing is shown just once. Perfect. I complete the grading design and start adding labels for the drainage inlets and pipes, using the Xref to label. Some time later I finish up adjusting all 250+/- labels, save the drawing, open the production drawing with the layouts, title blocks, details, into which said grading plan is xref'ed, and, wait, no labels on the drainage, oh, no pipoe network shown either. WTH? I look in the xrefs, and the pipe drawing is not listed. I go back to the grading drawing, and all is still good there. So I look in the XREF Manager, the Pipes drawing is now being shown as Overlay. I can't change it because it is a nested xref from the Roads drawing, in which is is still shown as Attached. So somehow, when I had Xref'ed the roads drawing containing the attached Pipe xref into my drawing already containing an attached Pipe drawing, the nested one was changed to Overlay...with no way to change it back. Even after I removed the original one, I could not ever get it to change. I 'fixed' it by importing all of the layouts and details into the Grading drawing, and turning it into a design/production drawing.
I hope this excercise in nested Xrefs helps someone else avoid the costly mistake I made....costly in that I spent ~2 hours trying to figure out how it happened and what I could do about it.
An important message indeed. I'll add it to my already lengthy list of why civil drawings should not use nested xrefs
Thanks so much for sharing that Jeff. I'm going to write that scenario up relating to the work that we do and perhaps do a lunch-n-learn to show our staff what happens. It's such a valuable tool to share that knowledge here as well as asking questions when we encounter a problem.
Is the conclusion to this to use Overlays only??
I think the conlusion is yours to make. All I could say is in 20 years I have experienced nothing but headaches, aggrivation and corrupt project files whenever xref nesting has been used. I forbid it.
No, I will still use nested xrefs (why xref my topo drawing into 30 Plan sheets when I can attach it once to the design drawing which is already xref'ed to those sheets?), I will just be much more careful about it. Until yesterday, I have never run into an issue with nested xrefs, and I've been using them since Xrefs were introduced way back when.
My xrefs are set in my prototype. When I maket a desin file or a sheet file all the needed xrefs are already there as overlays. Users can unload anything they dont need. It may not be the right way but it works for me