SDI - Serious Difficulties Increasing? (Bug Watch AutoCAD Tutorial)

31 Jul, 2008 By: Steve Johnson

How to encourage AutoCAD to open your old drawings, avoid a crash, deal with missing objects, and make AutoCAD 2009 a bit less sticky.

Open for the Best (2009)
I've seen quite a few complaints that AutoCAD 2009 refuses to open some drawings saved in 2000 or 2004 format unless the Recover command has been used on them. This is related to 3D materials and/or AEC data stored in the drawings by vertical variants of AutoCAD. Because there are many millions of drawings in this state, this is a significant problem.

Workaround: Autodesk has issued a Knowledge Base item about this problem. There's no real fix in AutoCAD 2009 yet, just an external workaround. You will have to fix up the drawings in AutoCAD 2008 or TrueView. To do this, either save the drawings in 2007 format or set the system variable 3DCONVERSIONMODE to 0 before saving them in the old format.

SDI Stumble 1 (2009)
To see this bug, you first need to set the SDI system variable to 1. This means you can open only one drawing at a time in a given AutoCAD session. I won't go into the possible reasons for doing this; please just take my word for it that there are still people around with legitimate reasons for doing so.

Now drag a drawing from Windows Explorer onto AutoCAD's title bar. AutoCAD will crash with the message "AutoCAD Error Aborting - FATAL ERROR: Unhandled Access Violation Reading 0x03dd Exception at a8d634h"

Workaround: None known other than "don't do that."

SDI Stumble 2 (2009)
Back in September 1996, in the dastardly dark days of Release 13, I asked, "Are parts of your drawings going AWOL? Some Release 13 users report that parts of their drawings disappear between saves and opens." That was caused by the then-new ISAVEPERCENT system variable, which was introduced to speed up file operations but which had unfortunate side effects. One of these was that it randomly made parts of some drawings go away. Changing that variable from its default value of 50 to 0 worked around the problem for those in the know.

In an eerie Release 13 / AutoCAD 2009 parallel, the new OPENPARTIAL system variable was introduced to increase the effective speed of a file operation (in this case Open), and it, too, has unfortunate side effects. I described one of them, Perilous Purge, in June. Here's another one. This can make parts of your drawings go away unless you set change the OPENPARTIAL system variable from its default value of 1 to 0. Fortunately, this particular bug occurs only if the SDI system variable is also set to 1.

To see this happen, first make sure SDI and OPENPARTIAL are both set to 1. Open a paper/model space drawing, make sure you're in a paper space layout with paper space current, and save the drawing. Now open the drawing, switch to model space and have a look around. Any objects that were not visible through the paper space viewports are gone!

Don't panic! The objects only look like they're gone. They're still there, as you can prove if you turn off OPENPARTIAL and reopen the drawing. But I can certainly imagine people who don't know what's going on throwing away the "corrupted" version of the drawing and going back to an earlier version, thereby losing lots of work.

Workaround: As I suggested in June, just set OPENPARTIAL to 0, preferably in a startup routine. If AutoCAD history is anything to go by, it should be safe to use after another release or two. In the meantime, don't trust it with your drawings.

Sticky Stuff 1 (2009)
One of the most painful bumps on the road for a new AutoCAD 2009 user is its "sticky" nature. It doesn't matter what benchmarks show, if a program introduces momentary pauses in its user feedback loop, then it will be seen as infuriatingly slow. Some people might think a half-second delay is insignificant, but waiting half a second for the cursor to respond to each mouse movement is intolerable. Some users have found AutoCAD 2009 too sticky to use and have given up in frustration.

One example of such stickiness can be seen when you are doing something as simple as drawing a line in an empty drawing. Start AutoCAD 2009, start the Line command and start picking points. After the second or third pick, your cursor will stick for a while before becoming responsive again. This happens the first time your cursor hovers over an object, which can include a line you just drew. The delay can be up to two seconds long, but even half a second can interrupt your flow and mess with your head.

Workaround: During that pause, AutoCAD is loading into memory the parts of the CUI file it needs in order to enable the new Rollover Tooltips feature to work. If you turn off that feature using the Options command's Display tab, this particular "stick" does not occur.

Look out for another sticky stuff removal tip next month!

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