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Maximum no. of generations in a GDG

 
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lucky.rohith
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Joined: 06 Aug 2006
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PostPosted: Thu Aug 24, 2006 12:50 am    Post subject: Maximum no. of generations in a GDG
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Hi,

Wht is the maximum no. of generations in a GDG,whether it is 255 or 9999?
wht is the difference between paging & swapping?
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superk

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PostPosted: Thu Aug 24, 2006 2:04 am    Post subject: Re: query reguarding GDG
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lucky.rohith wrote:
Wht is the maximum no. of generations in a GDG,whether it is 255 or 9999?


First, take a look here at Chapter 29. Processing Generation Data Groups in the z/OS V1R6.0 DFSMS: Using Data Sets manual, and

here at Topic 15. DEFINE GENERATIONDATAGROUP in the z/OS V1R7.0 DFSMS Access Method Services for Catalogs manual.

The maximum value for LIMIT when defining the GDG base is 255. The LIMIT determines how many generations can be accessed by relative access (i.e. 0, -1, -2,...-254, etc.). The settings for ERASE and SCRATCH determine what happens when the next cataloged dataset exceeds the specified LIMIT. With NOERASE and NOSCRATCH, the first cataloged dataset that exceeds the LIMIT will be "rolled out" of the Generation Data Group, but will still be cataloged, and the newest dataset "rolled in". With this setting, you can keep up to 9999 GDG datasets cataloged. Once generation 9999 is reached, the generation number rolls back to 0001.
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manishram1

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PostPosted: Sun Aug 27, 2006 5:04 pm    Post subject: Re: Maximum no. of generations in a GDG
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Really a good piece of information which we have to make a note of.
Thanks SuperK
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