oberman%icaen.DECnet@LLL-ICDC.ARPA ("ICAEN::OBERMAN") (06/28/87)
>Sorry if this Q has been asked before; I am not on the list, so please could >any replies be copied to me? thankyou. > >The DCL manual says that use of $SET FILE/ENTER is "discouraged" but >doesnt say why. Please could somebody kindly tell me why? What precautions >should I take if I go ahead & do it anyway? > >If asked I will explain why I want to do this, but I dont want to inflict >a very long explanation on the whole list. >mark Actually, I don't know of any recent discussion of this. So I'm posting it. File aliases are possible, but not supported in the ODS-2 disk structure. The problem is that if you create aliases (SET FILE/ENTRY) the file system thinks there are two files. If you delete one, the second is gone too. The directory entry remain, but it points off to nowhere. UNIX keeps a count, as I understand it, of aliased entries and does not actually delete a file until the count is 0. If you go ahead an do it, just be careful that the file is protected from accidental deletion and that if you want to delete it you delete all aliases first. Or at least all but one entry. There is no differentiation between the original and its aliases. DON'T delete all of the entries, as this will leave the file with no directory and it and its disk blocks are lost until an ANALYZE/DISK/REPAIR is done. R. Kevin Oberman Lawrence Livermore National Laboratory arpa: oberman@lll-icdc.arpa (415) 422-6955 Disclaimer: Neither my employer nor myself can take resposibility for the accuracy of this information. I believe it is correct, but if it's not I can only say "Sorry". I'm a rotten typist and a worse speller, so forgive any silly errors. ------
HIGHAMP@BYUVAX.BITNET (06/29/87)
Subject: Re: SET FILE/ENTRY As Mr. Oberman suggests, be careful when deleting files that you have created aliases for. Make sure that you use SET FILE/REMOVE to get rid of the extra names. The same restrictions apply in "removing" file names as do in deleting files. That is, you don't want to get rid of all of the names. An interesting sideline (or at least I think so)... We have a large cluster. One day I noticed that our system disk incremental backup was getting very huge. Three or four 2400 foot tapes at 6250, in fact. The problem, of course, was that the syscommon directories (which point to v4common) were all getting backed up as different directories. Each time the CDD would get changed, we'd get about 6 copies of it. My solution was to use /EXCLUDE on the backup to ignore the individual syscommon directories. I suppose that there is no economical way for DEC to fix this, but it certainly was a surprise. Dave Higham Signetics Corp. Orem, UT