2004

Increase Performance with Large Xrefs | 695
To unload an xref
1 From the Insert menu, choose Xref Manager.
2 In the Xref Manager, select an xref and then choose Unload.
3 Choose OK.
Reference toolbar
Command line
XREF
Work with Demand Loading
To realize the maximum benefits of demand loading, you need to save the
referenced drawings with layer and spatial indexes. The performance benefits
of demand loading are most noticeable when you do one of the following:
■ Clip the xref with AutoCAD to display a small fraction of it, and a spatial
index is saved in the externally referenced drawing.
■ Freeze several layers of the xref, and the externally referenced drawing is
saved with a layer index.
Note Clipped external references are available only in drawings created with
AutoCAD Release 14 or later.
If demand loading is turned on, and you have clipped xrefs that were saved
with spatial indexes, objects in the external reference database that are con-
tained within the clip volume comprise the majority of the objects read into
the drawing. If the clip volume is modified, more objects are loaded as
required from the reference drawing. Similarly, if you have xrefs with many
layers frozen that were saved with layer indexes, only the objects on those
thawed layers are read into the current drawing. If those xref-dependent
layers are thawed, AutoCAD reads in that geometry from the reference draw-
ing as required.
When demand loading is turned on, AutoCAD places a lock on all reference
drawings so that it can read in any geometry it needs to on demand. Other
users can open those reference drawings, but they cannot save changes to
them. If you want other users to be able to modify an xref that is being
demand loaded into another drawing, use demand loading with the Copy
option.