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For legacy reasons, my company must run certain programs that still make use of the 8.3 DOS filenames associated with the now more familiar long filenames. The file maintenance procedures in question are extremely stable, so I was surprised to discover an unusual condition when I backed up and restored certain files formatted with 8.3 filenames. Rather than describe the circumstances in detail, let me provide an example.
Suppose I create a directory that contains several similarly named files (in reality, these were financial audit files containing an automatically generated sequence number). I obtained the following directory listing for these files by typing dir /x at the command prompt:
Volume in drive C has no label. Volume Serial Number is B49D-A5D7 Directory of C:\Backup Test 05/31/99 11:27a
. 05/31/99 11:27a .. 05/31/99 11:22a 18 TESTFI~1.TXT TestFile1.txt 05/31/99 11:22a 17 TESTFI~2.TXT TestFile2.txt 05/31/99 11:22a 17 TESTFI~3.TXT TestFile3.txt 05/31/99 11:23a 19 TESTFI~4.TXT TestFile4.txt 6 File(s) 71 bytes 939,101,696 bytes free
If I delete one of these files (or change the filename so that it no longer conforms to the 8.3 base sequence) and type dir /x at the command prompt again, I get the following directory listing:
Volume in drive C has no label. Volume Serial Number is B49D-A5D7 Directory of C:\Backup Test 05/31/99 11:53a
. 05/31/99 11:53a .. 05/31/99 11:22a 18 TESTFI~1.TXT TestFile1.txt 05/31/99 11:22a 17 TESTFI~3.TXT TestFile3.txt 05/31/99 11:23a 19 TESTFI~4.TXT TestFile4.txt 5 File(s) 54 bytes 939,099,648 bytes free
Even though I've deleted TESTFI~2.TXT, the remaining files are still linked in sequence. Next, I backed up the directory to tape using NT Backup. If I later decide to restore this directory from the backup tape to a new directory or to the original directory, which has been cleared, I run into problems. (The latter option is important because the condition does not seem to occur when I restore the directory by overwriting or replacing existing files of the same long filename.) The effect of the restore is as follows:
Volume in drive C has no label. Volume Serial Number is B49D-A5D7 Directory of C:\Backup Test 05/31/99 11:57a
. 05/31/99 11:57a .. 05/31/99 11:22a 18 TESTFI~1.TXT TestFile1.txt 05/31/99 11:22a 17 TESTFI~2.TXT TestFile3.txt 05/31/99 11:23a 19 TESTFI~3.TXT TestFile4.txt 5 File(s) 54 bytes 939,098,112 bytes free
Notice that the DOS 8.3 names are now out of sequence with their associated long filenames. In my particular situation, this problem produced some unexpected results because the effects were more complex than what I've demonstrated in this simple example.
Although this feature might be well-known and documented, nobody else I have spoken with has considered the consequences. We can expect this problem will go away with the demise of DOS 8.3 filenames, but in the meantime, be aware if you still have legacy requirements.