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Data Generation Groups and renaming generations

 
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Paul Hacker

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Joined: 02 Oct 2008
Posts: 15
Location: Tyler, texas

PostPosted: Wed Jun 27, 2012 9:00 pm    Post subject: Data Generation Groups and renaming generations
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We have a GDG and one of the member files is badly allocated.

Example:
FAKEBKUP
FAKEBKUP.G0008V00
FAKEBKUP.G0009V00
FAKEBKUP.G0010V00
FAKEBKUP.G0011V00 <---
FAKEBKUP.G0013V00
FAKEBKUP.G0014V00
FAKEBKUP.G0015V00
FAKEBKUP.G0016V00
FAKEBKUP.G0017V00

And G0011V00 has 40 extents.

Now if I was to copy that to another DS with much better allocations and then delete the old G0010V00 and rename the new file to that name would it work? That is would any program using a FAKEBKUP(-5) pick up the new G0010V00 file.

I can also use IDCAMS to increase the number of members in the GDG so it does not drop off any.

Thanks!
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expat

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Joined: 14 Mar 2007
Posts: 8593
Location: Back in jolly old England

PostPosted: Wed Jun 27, 2012 9:05 pm    Post subject:
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Why not use HSM, or whatever DLM you have installed to migrate and recall the GENERATION - A member is something that lives in a PDS/PDSE
Title corrected - d
Why does it matter that the dataset has multiple extents ?
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Paul Hacker

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Joined: 02 Oct 2008
Posts: 15
Location: Tyler, texas

PostPosted: Wed Jun 27, 2012 10:34 pm    Post subject:
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Space expat, space!

And the files must be called back in order so we cannot have them out or order or the reports requesting certian time-line information won't be able to get the correct GDG dataaset.

This particular generation is used alot right now and thus kept off migrat. Oh, and it's only 39k cylinders!

thanks,
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dick scherrer

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Joined: 23 Nov 2006
Posts: 19270
Location: Inside the Matrix

PostPosted: Wed Jun 27, 2012 11:35 pm    Post subject:
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Hello,

Quote:
And the files must be called back in order so we cannot have them out or order or the reports requesting certian time-line information won't be able to get the correct GDG dataaset.
This surely needs clarification. . .

The multiple extents are not migrated separately (AFAIK). Either the entire dataset is migrated or it is not.

Whether the dataset takes only several extents or lots of them, the total space should be (about) the same.

Can you not work with your storage management people to give a "special" amount of time before migrating?
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vasanthz

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Joined: 28 Aug 2007
Posts: 1445
Location: Azeroth

PostPosted: Wed Jun 27, 2012 11:37 pm    Post subject:
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Hello,
Quote:
if I was to copy that to another DS with much better allocations and then delete the old G0010V00 and rename the new file to that name would it work? That is would any program using a FAKEBKUP(-5) pick up the new G0010V00 file.

I think yes, I tried deleting one of the GDG generations and created a new one with deleted generation's full name with the G0000v00. The -1,-2,-3... were getting resolved correctly.

LC command on the GDG base said that the deleted & newly created generation is already associated with the GDG base.
You could try it out, takes 5 minutes.

Hope it helps.
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superk

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Joined: 26 Apr 2004
Posts: 4648
Location: Raleigh, NC, USA

PostPosted: Thu Jun 28, 2012 12:02 am    Post subject: Reply to: Data Generation Groups and renaming members
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Copy the dataset and name it FAKEBKUP.G0011V01 (i.e. keep the same generation but change the version). That would keep it in the same relative position as the one replaced.
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daveporcelan

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Joined: 01 Dec 2006
Posts: 645
Location: Pennsylvania

PostPosted: Thu Jun 28, 2012 12:12 am    Post subject:
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Amazing, finally a valid use for a version other than V00.

Also finally a valid time to say VERSION.
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Paul Hacker

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Joined: 02 Oct 2008
Posts: 15
Location: Tyler, texas

PostPosted: Thu Jun 28, 2012 7:46 pm    Post subject:
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Ok guys the reason for all this is long time ago that particular GDG dataset was incorrectly allocated and takes up way to much space. 39000 cylinders and more extents than you can shake a stick at.

But due to it being needed to be read in sequence with the other GDGs it must stay in the same position so JCLs can read it in the right order.

G0011V01, never thought about that vasanthz. And then once it is copied and verified just get rid of the old G0011V00. Good idea!

But never do this near a weekend for real, especially with July 7th coming!

So I will experiment with my fake GDG today and if it's a go talk with the other geeks here and set up a time (I bet near midnight) to reconstruct the dataset.

Much thanks.
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dick scherrer

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Joined: 23 Nov 2006
Posts: 19270
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PostPosted: Thu Jun 28, 2012 8:22 pm    Post subject:
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Hello,

Good luck icon_smile.gif
Someone should be here if there are "opportunities".

Quote:
But never do this near a weekend for real, especially with July 7th coming!
Is July 7th a biggie there icon_cool.gif
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Pete Wilson

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Joined: 31 Dec 2009
Posts: 437
Location: London

PostPosted: Fri Jun 29, 2012 1:38 am    Post subject:
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Just run a DFDSS (ADRDSSU) COPY move job and it will try and allocate the file as a single extent, or as few as it can. Although why you're concerned about extents I have no idea, it is not a performance issue these days, to any significant degree. Remember Extended Format datasets can be up to 7257 extents. Check this out about extents, I certainly learnt alot from it: http://www.idug.org/conferences/EU2008/data/EU08A14.pdf

You don't explain why the allocation is bad. Is it because of the SPACE specified, or is it the DCB attributes, especially BLKSIZE? The DFDSS COPY can reblock the file as part of the move process as well. It can also release any allocated but unused space.

e.g.
COPY ALLE TGTA(SRC) CAT DEL PURGE REBL(**) -
DS(INC( -
FAKEBKUP.G0011V00 -
))

Or even better, leave it alone!
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