If a drawing file is damaged, you can recover some or all of the data by using commands to find and correct errors.
When an error occurs, diagnostic information is recorded in the acad.err file, which you can use to report a problem.
A drawing file is marked as damaged if corrupted data is detected, or if you request that the drawing be saved after a program failure. If the damage is minor, sometimes you can repair the drawing simply by opening it. Otherwise, you can use the following:
Auditing a file generates a description of problems with a drawing file and recommendations for correcting them. As you start the audit, you specify whether you want the program to try to fix the problems it encounters. The report is similar to the following example:
DXF NAME Current Value Validation Default
PDMODE 990 - 2040
UCSFOLLOW 811 or 0
Error found in auditing header variables
4 Blocks audited
Pass 1 4 objects audited
Pass 2 4 objects audited
Total errors found 2 fixed 2
If you chose not to correct the errors, the last statement changes to
Total errors found 2 fixed 0.
AUDITCTL system variable is set to 1 (On).The output from a recovery audit is written to an audit log (ADT) file if the
Recovery does not necessarily preserve the high-level consistency of the drawing file. The program extracts as much material as it can from the damaged file.