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AutoCAD is a vector based
drawing program. It keeps a database describing the properties of
every element placed in the drawing by the drafter. The screen
representation in the drawing editor is just that - a representation
of what is in the database.
From
time to time the drawing database can become corrupt and a drawing will
start behaving badly. This may be due to a number of reasons:
Duplicate elements in the
database,
Exploded
hatching can sometimes give problems,
Phantom
elements such as hatching.
You
may get messages such as "Unable to continue - autosave?". This may be an indication that the drawing database
has become unstable.
Recognizing this, Autodesk (from about Release
12 onwards)
provided an AUDIT function (command). This command should be used from time to
time to check the integrity of the drawing database.
 Early
versions of AutoCAD LT did not implement the command, but later versions
of AutoCAD and IntelliCAD certainly do.
The
AUDIT command is a diagnostic tool for examining the current drawing and correcting
errors. For every error detected, AutoCAD provides a description and
recommends corrective action.
For
easy access, AUDIT places all objects for which it reports errors in the 'Previous'
selection set. A quick issue of the MOVE command with the P
option chosen, will show just those those entities that have been adjusted by the use
of the audit command.
Note
that editing/audit commands affect only the
objects belonging to the current paper space or model space. You need to
audit in both paper space and model space.
When
the AUDITCTL system variable is on, AUDIT creates an ASCII file containing
a description of the problems and the actions taken.
This report file is
placed in the same directory as the current drawing and given the file
extension .adt. If you want to open this file, use Windows NotePad.
If
a drawing contains errors that AUDIT can't fix, the RECOVER command
can be used to retrieve the drawing and correct its errors.
Be
especially careful with drawings that have external references attached.
Using the Audit command may fix problems in the current drawing session, but when
the drawing is saved and reloaded, those very same errors will appear
again because they are buried in the XREF(s).
This can be very frustrating indeed.
It
is a good idea to 'flip' to the text window when you are having
problems with a drawing. Errors
in the drawing display in the text window (F2 in Windows, F1 in
DOS).
Every
entity in an AutoCAD drawing is assigned a 'handle'. If
any of the errors are handle or 'handseed' errors, you can fix the handles. If the
drawing is used over and over, the number of handles can exceed the
maximum number allowed and cause problems. You can test to see if the
drawing is near or has exceeded the number of handles allowed. If you have
found possible handle errors using either the AutoCAD audit or this test,
then after you wblock the drawing, you should fix the 'handseed' errors.
Place
a primitive element such as a circle in the drawing.
At
the Command prompt, type the LIST command, and press ENTER.
Select
the circle and press ENTER twice.
The properties of the circle display in
the text window. If
there is a Handle= number in the list, count the number of characters in
that number. If
the number is 15 or 16 characters long, you may have handle
problems.
Erase
the circle.
One
method to clean up problem drawings that auditing does not fix, is
to use the WBLOCK to
create a new drawing from the problem one. Then insert that drawing
into a freshly created blank drawing file.
If your drawing uses paper
space, you must wblock the paper space objects separately.
To
clean a drawing that does not use paper space:
Open
the drawing.
At the Command prompt, type wblock, and press ENTER.
In
the Create Drawing File dialog box, under File Name, type a new
drawing name, and click OK. (Remember which directory the drawing
is going into.)
At the Block Name prompt, type *, and
press ENTER. All objects in your drawing are exported to the new
drawing.
Create
a new drawing.
At
the Command prompt, type ddinsert, and press ENTER.
In
the Insert dialog box, click File.
In
the Select Drawing File dialog box, under File Name type the
drawing name you just created, and click OK.
In
the Insert dialog box, select the Explode box, and click OK.
At
the Insert point prompt, type 0,0, and press ENTER three
times.
The objects are imported into the current drawing.
To
wblock the model space objects:
Open
the drawing.
At
the Command prompt, type tilemode 1, and press ENTER.
At
the Command prompt, type wblock, and press ENTER.
In
the Create Drawing File dialog box, under File Name, type model,
and click OK.
At
the Block Name prompt, type *, and press ENTER. The
objects in model space are exported to the new drawing.
To
wblock the paper space objects:
At
the Command prompt, type tilemode 0, and press ENTER.
If
the drawing is not in paper space, type pspace, and press ENTER.
At
the Command prompt, type wblock, and press ENTER.
In
the Create Drawing File dialog box, under File Name, type paper,
and click OK.
At
the Block Name prompt, press ENTER.
At
the Insertion Point prompt, type 0,0, and press ENTER.
At
the Select Objects prompt, select all the objects in paper space,
and press ENTER.
Now
start a new drawing, switch to tiled model space and bring in the
model space entities, switch to paper space and bring in the paper
space entities.
Create
a new drawing from the File menu, and click New.
In
the Save Changes to . . . query box, click No.
At
the Command prompt, type ddinsert, and press ENTER.
In
the Insert dialog box, click File.
In
the Select Drawing file dialog box, under File Name, type model,
and click OK.
In
the Insert dialog box, select the Explode box, and click OK.
At
the Insert point prompt, type 0,0 and press ENTER three
times.
Get
into paper space: at the Command prompt, type tilemode 0, and press
ENTER.
At
the Command prompt, type ddinsert , and press ENTER.
In
the Select Drawing file dialog box, under File Name, type paper ,
and click OK.
In
the Insert dialog box, select the Explode box, and click OK.
At
the Insert point prompt, type 0,0 and press ENTER three
times.
At
the Command prompt, type mview , and press ENTER.
At
the ON/OFF/Hideplot/&ldots;/<First point> prompt, type on,
and select the viewports in paper space. At
the Command prompt, type regenall to regenerate all the viewports.
Use
AUDIT at the end of every drawing session. Do not continue working with
drawings that fail the audit test.
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