ncperson@ndsuvax.UUCP (Missing Person) (07/29/88)
Can anyone tell me why DOS will sometimes overwrite the directory of obe floppy with that of another? I've had this happen several times in the last week. it seems to simply be replacing the directory information with a copy of what was on the previously inserted disk. I've heard of this happening before, but have never heard why it happens. Can somwone enlighten me? thaks . -- Brett G. Person North Dakota State University uunet!ndsuvax!ncperson | ncperson@ndsuvax.bitnet
Ralf.Brown@B.GP.CS.CMU.EDU (07/29/88)
In article <1060@ndsuvax.UUCP>, ncperson@ndsuvax.UUCP (Missing Person) writes: }Can anyone tell me why DOS will sometimes overwrite the directory of }obe floppy with that of another? I've had this happen several times in the }last week. } it seems to simply be replacing the directory information with a copy of }what was on the previously inserted disk. I've heard of this happening before, but have never heard why it happens. Can somwone enlighten me? What is happening is that you are switching disks while there are still files open on the first disk. As long as files are open, DOS will not flush its disk buffers and update the directory and FAT. When you then put in a different disk, DOS doesn't read the new directory and FAT (since it thinks it already has them), and the next directory update writes out the directory of the old disk onto the new one. The cure is to make sure that all files are closed before switching disks. Note that some programs which use overlays keep files open until the program terminates. ProComm 2.4.2 is one such program, and it uses the Plink overlay linker, so presumably all programs linked with that linker will show the problem. Running 'strings' on the file should show you the Plink copyright notice on programs using it. -- UUCP: {ucbvax,harvard}!cs.cmu.edu!ralf -=-=-=- Voice: (412) 268-3053 (school) ARPA: ralf@cs.cmu.edu BIT: ralf%cs.cmu.edu@CMUCCVMA FIDO: Ralf Brown 1:129/31 Disclaimer? I |Ducharm's Axiom: If you view your problem closely enough claimed something?| you will recognize yourself as part of the problem.
len@csd1.milw.wisc.edu (Leonard P Levine) (07/30/88)
From article <1060@ndsuvax.UUCP>, by ncperson@ndsuvax.UUCP (Missing Person): > Can anyone tell me why DOS will sometimes overwrite the directory of > obe floppy with that of another? I've had this happen several times in the > last week. > it seems to simply be replacing the directory information with a copy of > what was on the previously inserted disk. I've heard of this happening before, >but have never heard why it happens. Can somwone enlighten me? > thaks . If you were working with a 1.2 meg floppy, the problem is with the inability of your system to detect the removal of the media. for the 360K drive, the system will not recheck the directory if you reuse the disk in less than 2 seconds from the last use. Are you working that fast? + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + | Leonard P. Levine e-mail len@evax.milw.wisc.edu | | Professor, Computer Science Office (414) 229-5170 | | University of Wisconsin-Milwaukee Home (414) 962-4719 | | Milwaukee, WI 53201 U. S. A. Modem (414) 962-6228 | + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
creps@silver.bacs.indiana.edu (Steve Creps) (07/30/88)
In article <6332@uwmcsd1.UUCP> len@csd1.milw.wisc.edu (Leonard P Levine) writes: >From article <1060@ndsuvax.UUCP>, by ncperson@ndsuvax.UUCP (Missing Person): >> Can anyone tell me why DOS will sometimes overwrite the directory of >> obe floppy with that of another? ... >> it seems to simply be replacing the directory information with a copy of >> what was on the previously inserted disk. I've heard of this happening before, >If you were working with a 1.2 meg floppy, the problem is with the inability >of your system to detect the removal of the media. >for the 360K drive, the system will not recheck the directory if you reuse the >disk in less than 2 seconds from the last use. Are you working that fast? I believe this is actually a bug (or inconvenience) in DOS. I've also seen this happen before, usually when the disks were changed before exiting whatever program happened to be running at the time. At least, in my opinion it was an unfortunate choice to allow DOS to buffer changes to the disk directory, which I would guess is what is happening to cause the problem. As for the system being able to detect a disk change, this feature is not present in PCs or XTs. According to Norton's programmer's guide, DOS interrupt 13H service 16H is specific to ATs. The reason I note this is because when I've seen this happen, it has been on a PC or XT. Comments welcome, a lot of what I've just said is hypothesis. - - - - - - - - - - Steve Creps, Indiana University, Bloomington, home of the "Hoosiers" creps@silver.bacs.indiana.edu (192.12.206.2) {inuxc,rutgers,pyramid,pur-ee}!iuvax!silver!creps creps@iubacs.bitnet (forwarded)
vojta@BOSCO.BERKELEY.EDU (07/30/88)
In article <1060@ndsuvax.UUCP> Brett G. Person writes: |Can anyone tell me why DOS will sometimes overwrite the directory of |obe floppy with that of another? I've had this happen several times in the |last week. | it seems to simply be replacing the directory information with a copy of |what was on the previously inserted disk. I've heard of this happening before, but have never heard why it happens. Can somwone enlighten me? |thaks . |-- |Brett G. Person |North Dakota State University |uunet!ndsuvax!ncperson | ncperson@ndsuvax.bitnet it does this if you try to write to a write-protected disk, receive the infamous "...Abort, Retry, Ignore" message, switch the disks, and respond with 'r'. The solution in this case is to abort and start over. Hope this helps.
chasm@killer.DALLAS.TX.US (Charles Marslett) (08/05/88)
In article <1060@ndsuvax.UUCP>, ncperson@ndsuvax.UUCP (Missing Person) writes: > Can anyone tell me why DOS will sometimes overwrite the directory of > obe floppy with that of another? I've had this happen several times in the > last week. > it seems to simply be replacing the directory information with a copy of > what was on the previously inserted disk. I've heard of this happening before, but have never heard why it happens. Can somwone enlighten me? > thaks . > -- > Brett G. Person The copying of the FAT and/or directory from one disk to another is a result of DOS failing to realize that the diskette that was in there is removed and has been replaced. Some PCs (like the true blues) have sense information that let them know if the diskette has stopped spinning -- so no real extra effort is needed to be fairly sure of a "media change". Other hardware does not have this extra bit of data available, so the BIOS usually decides a "media change" may have taken place if not I/O to the drive has been active in perhaps 1 or 2 seconds. Then it makes sure of the fact by comparing some data on the diskette with internal copies of that same area of the disk (assuming no two diskettes will match) -- I think this is a chunk of the FAT, but I may be wrong). A bit of a kludge, but it often works !?!? (:^}]. Charles Marslett chasm@killer.dallas.tx.us > North Dakota State University > uunet!ndsuvax!ncperson | ncperson@ndsuvax.bitnet