[cctalk] Re: IBM VM "CMS" tape format

-----Original Message----- From: Chuck Guzis via cctalk <cctalk(a)classiccmp.org> Sent: Thursday, September 21, 2023 3:39 PM To: Dennis Boone via cctalk <cctalk(a)classiccmp.org> Cc: Chuck Guzis <cclist(a)sydex.com> Subject: [cctalk] Re: IBM VM "CMS" tape format I slept on the problem a bit--good thing that I'm old; I like to sleep--and think that I've got it sussed out. Tape appears to consist of 4101 byte blocks, each with a "/02CMSx" header; the first one seems to be "CMSF" with the intervening ones being "CMSV" and then a final 87 byte block starting with "/02CMSN" and with what appears to be file metadata, including the file name. The body of the 4K+ blocks appears to be 80 character card images. Last block of each file seems to be padded with nulls. I'll dig into it a bit today, but I believe that I'm on the right track. Unfortunately, the data itself is client-proprietary, so no sharing there, sorry. What threw me was that there are 5 physical files on the tape (i.e. blocks separated by tapemarks), so I was expecting something logical. Silly me. Thanks, Chuck