MVS TOOLS AND TRICKS OF THE TRADE MAY 2008 By Sam Golob and Courtney Taylor -- --- ----- --- -------- ------ Sam Golob MVS Systems Programmer P.O. Box 906 Tallman, New York 10982 Sam Golob is a Senior Systems Programmer. He also participates in library tours and book signings with his wife, author Courtney Taylor. Sam can be contacted at sbgolob@cbttape.org. Information about the CBT MVS Tapes can be found on the web, at http://www.cbttape.org. PRESERVING YOUR TAPES FOR POSTERITY Over the nearly 30 years that I've been in this field, most people who've worked with us and talked with us have taken "progress" for granted. Everything has been improved. The hardware is always getting better and faster. The disk drives are getting better, bigger, and faster. The old clunker green-screen terminals have been taken over by multi-color emulators running on the PC. And, of course, software developments abound, both in the operating system software, and in the application software. Recently, the software that is avalable for the PC's themselves, has taken several quantum leaps forward, so it seems. And the new capabilities of the hand-held computers and mobile phones blow the mind away. Modern times sure are exciting! How does all this reflect on the world of tapes? Let's think about it. Tapes were always the "overflow medium" and the "archive medium" for MVS systems. In the early days, tapes had bigger capacities for holding data than did disk packs. So when you wanted to back up or preserve the data on disk packs, you'd back them up to tape. Now, with "redundant copying" of data on disks, with bigger and faster disks, with "virtual tapes" that are really disk files, and with far faster data transmission speeds to duplicate current data at remote locations, it's developing that people are really moving away from the concept of using tapes for archiving data. MVS (read z/OS) installations are having a tendency to keep fewer and fewer tape drives. In the current atmosphere, we've even heard of some installations who are considering getting rid of all, or most of their tape drives altogether. This doesn't mean that tapes are getting useless. First of all, a tape backup will preserve a "snapshot" (so to speak) of the contents of a disk AT ONE PARTICULAR TIME. Having a record like that can be very important. It's nice to know that there is a stable recording or a stable "level" of the "ever changing" disk pack archived somewhere, that you can refer to. But now we'll delve into another aspect of tapes and their "technology", which is far more consequential and relevant to us. I'd say that this following observation is the main point of our article. THE IMPACT OF THE P/390 AND HERCULES ON "TAPES" There's this point to make. Ten years ago, who would've thought that my PC at home would be able to emulate hardware, and even run an old copy of the MVS operating system? Well today, it's a reality. Not only does the commercial FLEX-ES (TM of Fundamental Software) system (most of the "development ones" are currently expiring as we write) emulate IBM hardware on a PC, but even the open-source Hercules system can do it too. Legally, you can download and operate an old 1975-level MVS on Hercules at home, for free. And since there are a good many retirees and other interested parties constantly improving that old MVS (it supports 3380s and 3390s now, and there are ISPF-like file editors for it), it's rapidly becoming a practical "new environment" for seasoned MVS practitioners to work in. All of their saved tapes from 20 and 25 years ago, are suddenly becoming "relevant" again. But our additional observation is, that this Hercules system, and the improved old MVS system which legally runs with it, can read virtual, AWS-format tapes as though they were real tapes. What does that mean to us? Well, when IBM developed their P/390 systems (in the 1990s) as a hardware platform to run MVS on a PC, they had to make a "virtual tape" format which simulated a tape, on a disk file. Not everyone had real tape drives that they could attach to a PC. (One drive would cost about 12K dollars at that time.) Since IBM's prefix to designate the P/390 software (IBM always has a prefix) was "AWS", their format of disk file which imitates a tape, is called AWS-format by most people. I think that the FLEX folks came up with that term first, because they wanted to differentiate IBM's P/390 tape format from their own Faketape (TM) virtual tape format. Anyway, once there's AN ACCESSIBLE disk format to represent an entire tape, people can start using it independently. This contrasts with the disk formats for Virtual Tape libraries, which are proprietary. AWS tape format is not proprietary. Anyone can make "tapes" in this format, which is public knowledge. You don't need to have a P/390 machine either. If you have tapes in AWS format, there are several ways in which you can read them. First, Hercules recognizes virtual tapes in AWS-format as being "tapes". So if you have a running Hercules system, you can mount the AWS-format tapes on that system using a "devinit" command, and you can run a TAPEMAP job or other such job against the AWS-format tape file, as though it were a real tape. Another way of directly looking at an AWS-format tape on the PC, is by using David Trout's (www.softdevlabs.com) AWSBROWSE program on a Windows machine. I've packaged this program on CBT Tape File 782 (www.cbttape.org - please look on the Updates page) as a .zip file which unzips to an .exe file that should be installed on Windows. Because the CBT Tape files are intended to be used on an MVS system, the installation of this one, which is intended to be used on a Windows machine, is a bit awkward. Here's how it goes. File 782 should be uploaded to MVS in BINARY. Do a TSO RECEIVE with the INDS( ) parameter on MVS into a pds. Then you download the AWSBR152 member of the pds, in BINARY, back down to the PC. After unzipping that on the PC, you get an .exe file, which you can install on Windows. The AWSBROWSE program, once installed on the PC, will allow you to view all the blocks, and label information, on the AWS-format tape file. Go to www.cbttape.org on the Updates page, and get AWSBROWSE for yourself. David Trout's website, www.softdevlabs.com, also has the latest and greatest AWSBROWSE program (much easier to install). What can you do to handle AWS-format "tapes" on a "pure MVS" system? Plenty. On CBT Tape File 533, there is a set of utilities to make a "real tape" from an AWS-format tape, and vice-versa. The one point is that on MVS disk, the AWS-format tape must be folded over into an FB (fixed block) disk dataset with record length (LRECL) equal to 80 (but with any block size that is a multiple of 80). That can be accomplished by FTP-ing the AWS file from the PC up to the mainframe, in BINARY, into an FB-80 dataset. The folding over will be accomplished automatically by FTP. Then the VTT2TAPE program from File 533 will read the folded-over AWS format file, and cut a real tape from it. The VTT2DISK program will do the opposite, and will create a folded-over FB-80 AWS-format tape file from a real tape, which can then be FTP-ed down to a PC file. So it results that if you use the VTT2TAPE utility to convert an AWS-format "tape" into a real tape, and the VTT2DISK utility to do the opposite, the two media would become interchangeable. And furthermore, if you had a Hercules system running on your PC, at home or at work, even if it is running the old free MVS from 1975 (but improved), you can still map the AWS-format tapes directly, and look at their contents, before trying to convert them to real tapes for z/OS use. To obtain a copy of VTT2TAPE and VTT2DISK and related programs, go to www.cbttape.org, look first at the Updates page and then at the CBT page, and download File 533 from there. Now, the consequence would be, that instead of having to save tapes, you could save PC AWS-format disk files on cd-rom or DVD. These take up far less physical space than even a cartridge does, and anybody with an inexpensive DVD or CD duplicator machine can make backup copies of them. (We just bought a 5-tier DVD duplicator for $449. Works fine.) Therefore, even if you are worried that a cd-rom or DVD might not last, when you have 2 or more duplicates of them, you're somewhat safer. And if you have a standalone DVD duplicating machine, you're even better off! Just to show you an example of how good this technology is, we have just made one DVD that contains probably 100 tapes on it, including 40 back-level CBT Tapes, all zipped. These are the wonders of modern technology. In our opinion, that should change people's thinking. At least, you personally should save your own "favorite tapes" from your collection, in this way, even if these methods still might be deemed impractical at a corporate level. KEEPING FUTURE DEVELOPMENTS IN MIND We have seen that if you have entire tapes in AWS-format, stored away on CD, on DVD, or on PC disk, you can either read them with a Hercules system, browse them on the PC using David Trout's AWSBROWSE program, or convert them to real tapes on any MVS system, using the VTT2TAPE program from CBT Tape File 533. Even today, these alternatives allow you to store your tapes away as PC disk files, and to use them profitably when you'll need them. But there is one missing piece. That is, you currently (at this time) can't treat an AWS-format "tape file" with a native MVS (z/OS) system, as though it were a real tape. My take on this situation is as follows. Future developments will open up new possibilities. For example, if someone develops a subsystem that will allow MVS to read AWS-format tape data as though it were a real tape, then using just minor changes in JCL, you'll be able to directly run all MVS-based tape programs against an AWS-format tape file, just as though it were a real tape. So then, you'll be able to directly TAPEMAP an AWS-format tape file that's on MVS DASD, or you'll be able to copy it with the COPYMODS program (CBT Tape File 229) or any other tape copying program, to either a real tape, or to another AWS-format tape image. This hasn't been written yet, but as soon as it HAS been done, and it's in place and debugged, a whole world of "tape manipulation" possibilites will then be opened up. So you can see why it pays (even now) to save your tapes as PC files, in AWS format. When this stuff gets developed (and it will), you'll then have a whole world of things to do with your AWS-format tapes! We're simply saying that "vaporware" doesn't always stay vaporware. It gets developed, through the efforts of concerned people, and then all of us can get the benefit. CONCLUSION We're saying, yet again, that when technological developments come, they require a rethinking of our methods. New technology opens up new possibility. Having a 4.7 gig DVD, and the possibility of representing entire tapes, from end to end, in the publicly available AWS disk format, allows us to store the complete contents of many tapes on one small disk. Having inexpensive DVD disk duplicators available, makes the preservation of all of this data much easier. And with more tools to "read" this data constantly being written, it pays to save our tapes in this format, so we will be able to use their contents far into the future. We wish all of you a good and happy month, and we're looking forward to seeing you here again, next time.