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
