1. Why these many considerations (I know it's a poorly phrased question but I, for the one, is declared as "glutton for punishment"-- so 'am ready..)?
2. I understand, DASDs and Tapes are different animals altogther. But in many programs at my shop, output files are tape files. And when I need to "dump" them I use MULTIGEN, which is actually an in-house utility. But the question is -- tape file is created by an application program so how would above consideration can be utilized for such a tape-file?
Joined: 06 Jun 2008 Posts: 8214 Location: Dubuque, Iowa, USA
Anuj, in one sense a tape is a tape is a tape. In another sense, not all tapes are created equally. For example, using ADRDSSU (DF/DSS) to back up an application file (or system file, or any file) makes sense as ADRDSSU is designed to be IBM's back up and restore utility. However, ADRDSSU files are formatted in a special way and you cannot recover them using any tool but ADRDSSU. In fact, you cannot even copy the tape to another tape without using the ADRDSSU utilities -- or the copied tape will not be usable for any restore operations.
IEBCOPY unloads a PDS to a sequential file basically by adding 16 to the block size to get the LRECL, changing the format to VS, and dumping the data. Hence, a PDS that is FB, 80, 6160 will unload into a VS, 6176, 6180 tape file -- so IEBCOPY will be required to restore the file; an application program most likely won't be able to interpret the format.
Data files created by an application are generally simple data files and can be dumped using IDCAMS, IEBGENER, or an in-house utility as you mention. But different utilities do things with tape files that don't always look right at first; understanding the different utilities helps pick the right one for the task at hand.