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In order to copy from tape to disk, you must know how the...

 
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Anuj Dhawan

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Joined: 22 Apr 2006
Posts: 6258
Location: Mumbai, India

PostPosted: Tue Jul 21, 2009 6:13 pm    Post subject: In order to copy from tape to disk, you must know how the...
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Some one has correctly said.. it's not easy to deal with System Programmers and when you have little experience it's rather tough... icon_smile.gif

Please have a look on the below thread, I've linked the thread with the "text of intreset" from that thread...

In order to copy from tape to disk, you must know how the tape was created. If the tape was created using DF/DSS (ADRDSSU), then you must use ADRDSSU to restore the data set from tape to disk. A PDS copied to tape will be in IEBCOPY unload format (which is a sequential file, usually in variable blocked spanned format). If the tape file is fixed block, then IEBGENER or SORT was used to create a copy of a disk data set. However, there's a lot of ways to build a tape and you cannot always tell from inspection how the tape was built and how to restore the tape to disk.

Now the questions are

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?
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Robert Sample

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Joined: 06 Jun 2008
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Location: East Dubuque, Illinois, USA

PostPosted: Tue Jul 21, 2009 6:33 pm    Post subject:
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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.
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Anuj Dhawan

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Joined: 22 Apr 2006
Posts: 6258
Location: Mumbai, India

PostPosted: Wed Jul 22, 2009 5:25 pm    Post subject:
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Thanks Robert -- that helps.

As an application programmer I usually deal with tape-data files created by an application, so consideration about ADRDSSU and IEBCOPY were quite distant.

Thanks again -- this topic goes under "Set a bookmark for this topic". icon_smile.gif

Regards,
Anuj
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