I am a bit late in coming to this. You probably want to look at DFSMS Using Data Sets. The one that I will be referencing is SC26-7410-11.
Page 553 has a title "Using the POINT Macro to Position to a Block" Please notice TYPE=ABS. This allows you to go to an absolute block. If you use REL, it is a relative block situation and can take a very long time to complete. This particular issue came about when a customer noted that it was taking an inordinate amount of time to reposition a tape on a restart of a file transfer for Connect:Direct (back when I worked on C:D z/OS). We (Sterling Commerce) had been using RELative offsets, having missed this little item. It was taking as long to restart with tape as it would have to just start over (particularly with those >50GB cartridges - I forgot the model number of the ones where we discovered this). Now there are some regression tests on an ATL for this ( ;-) ). Also, at the time that this was fixed, I was dealing with IBM (Sterling had not yet been acquired by IBM) on a different TAPE issue. Somewhere IBM had announced that EXCP was no longer being supported (I asked point blank when and where that was announced - still waiting for that answer ;-) ). Apparently that support had been withdrawn when ATLs were using the next drive after 3490 "heads". So I got out the hardware manuals the CEs use and started reading. The underlying tape units are SCSI and it appears that there is not a one for one correspondence between the CCW commands and the SCSI commands. So EXCP support for tape was ended in Connect:Direct for TAPE. However, EXCP is still used to read the tape labels (only way to do this efficiently). So if you have issues with non IBM code doing EXCP to tape, you may find that IBM won't be of much help (just a little heads up here). I hope this helps you with what you are attempting to do. Regards, Steve Thompson The information transmitted is intended only for the person or entity to which it is addressed and may contain CONFIDENTIAL material. If you receive this material/information in error, please contact the sender and delete or destroy the material/information. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
