Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site drivax.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!zehntel!hplabs!amdahl!drivax!steve From: steve@drivax.UUCP (Steve Williams) Newsgroups: net.eunice,net.unix-wizards Subject: Re: Question about mag tapes under Eunice Message-ID: <62@drivax.UUCP> Date: Fri, 7-Dec-84 02:01:48 EST Article-I.D.: drivax.62 Posted: Fri Dec 7 02:01:48 1984 Date-Received: Mon, 10-Dec-84 01:44:12 EST References: <162@prcrs.UUCP> Distribution: na Organization: Digital Research, Monterey, CA Lines: 35 Xref: watmath net.eunice:188 net.unix-wizards:10870 > Maybe someone can enlighten me as to why this works the way it does: > > My wife works on a Eunice system (version 3.2). I gave her a mag > tape with some stuff written on it in tar format (V7 tar, 1600 bpi). > She was able to extract it using tar on her Eunice machine with no > problems. She then put some things on the tape to give me, again, > using tar. She had no problem putting things ON the tape, but when > she tried to get a table of contents listing, tar complained about > the block size being zero and no TOC was generated. She recreated the > tape with tar, only this time put a blocking factor (tar cvb 20 files). > Again, there was no error, but when she tried a TOC, the same error > happened. At this point, she gave up and gave the tape back to me. > I mounted the tape on my machine and managed to generate the TOC AND > extract the tape with no problems (and yes, the files were the files > that SHE put on the tape, not the ones I put on). I don't understand.. > > Why is that VMS/Eunice can't read its own writing? The default block size on a tape mounted with the VMS /FOREIGN switch is 512. To read a blocked tar tape, you need to set the block size to a value greater or equal to the block size on the tape. For tar b 20, the block size is 20 x 512 or 10240. Magic incantations which are known to work:: $ mount mtxx:/for/block=65534 (te16) $ mount mfxx:/for/block=65534 (tu7x) 65534 is the maximum value for the /block parameter. This allows you to read the tape even if you don't know the blocksize. -Steve Williams {ihnp4,mot,ucscc,amdahl}!drivax!steve