https://www.ibm.com/docs/en/zos/2.4.0?topic=up-syntax-1
//ddname DD DISP=SHR,DSN=hlq.data.set.name1.llq, // UNIT=(tape,2) * device,count // DD DISP=SHR,DSN=hlq.data.set.name2.llq, // UNIT=AFF=ddname * repeat as needed On Fri, Jan 10, 2025 at 6:02 PM Farley, Peter <[email protected]> wrote: > > I have a business need to scan 15 different tape files (all the same record > format, some are multi-volume) to extract relevant information, and I first > tried to scan them all in one concatenated DD. I didn't specify anything but > DISP and DSN for each file in the concatenation, so I got 15 tape mounts to > 15 different tape drives. > > I would like to limit the tape drive usage so as not to unintentionally > interfere with production work that actually needs a tape drive. Using > UNIT=AFF=INPUTDD on the second and all other DD's in the concatenation limits > usage to ONE tape drive, the one allocated to the first file in the > concatenation. > > In order to reduce elapsed time for the scan job (each tape dismount/mount > operation takes an appreciable amount of time, usually at least a minute or > so), is there any way to use TWO drives in one concatenated DD instead of one > drive, so that as each file reaches EOF the process continues with the > already-mounted next file while the system loads the EOF drive with the next > file? If I knew in advance the device numbers of tape drives that are > actually available I could try to use UNIT=device1 and UNIT=device2 on > alternating DD's, adding ",,DEFER" to all but the first two DD's, but I don't > know what drives are available before I submit the job. > > If there is a way to use two drives without knowing the device numbers ahead > of time, what happens if one of the tape DD's is a file that has multiple > volumes? Does an already-mounted file from the next DD get dismounted to > load the next volume of the one being processed, or does it dismount the > first volume and wait for the next volume to be mounted on the same drive? > > These aren't "real" drives of course, they are all in a VTL, but the > principal is the same - don't occupy more devices than you really need. > > Peter > > This message and any attachments are intended only for the use of the > addressee and may contain information that is privileged and confidential. If > the reader of the message is not the intended recipient or an authorized > representative of the intended recipient, you are hereby notified that any > dissemination of this communication is strictly prohibited. If you have > received this communication in error, please notify us immediately by e-mail > and delete the message and any attachments from your system. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
