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relation b/w Retention and limit for GDG's

 
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smita V

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Joined: 05 Nov 2007
Posts: 11
Location: hyderabad

PostPosted: Tue Jul 22, 2008 3:42 pm    Post subject: relation b/w Retention and limit for GDG's
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Hi,

I want to know the how the limit and retention period for GDG datasets works in relation to each other.

I am assuming that by retension period we are meaning the numbers of days each GDG version of a particular cluster will be available and Limit as the number of GDG versions that we can have for max. Correct me if I am wrong.

If I am keeping the Limit as 3 and Retension period as 10 days using FOR parameter while defining a cluster and creating a new version each day.

Then on 4th day will the fourth generation will be created since the limit is 3? and if it happens what will happen to the first version of the GDG, the retention period of which is not met on 4th day.

Iam using SCRATCH option while defining the cluster.

Thanks,
Smita
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expat

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

PostPosted: Tue Jul 22, 2008 3:49 pm    Post subject:
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1) I assume that by CLUSTER that you really mean GDG base
2) I also assume that you mean to say generations rather than versions. Generations and versions are both valid terms in GDG parlance, but have totally different meanings

What happend to gen 0001 when 0004 is created - well to be real picky this is a site specific question as what happens to gen 0001 will depend on how your storage people have set up the SMS environment.

They may have set it up to honor your 10 day retention by retaining the deleted gens in ROLLED OFF status, or they may have set it up to ignore user supplied retention (I always do icon_lol.gif )

Also there may be backups available which will honour the 10 day retention of each generation. Either that or actually try it yourself and see what happens.

The very best bet is go talk to your storage people to get the info that you require.
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Anuj Dhawan

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

PostPosted: Tue Jul 22, 2008 4:04 pm    Post subject:
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Hi,

Trying to take the exapt's legacy little more ahead -

Quote:
I am assuming that by retension period we are meaning the numbers of days each GDG version of a particular cluster will be available and Limit as the number of GDG versions that we can have for max. Correct me if I am wrong.
Term "Retention period" is not limited to GDGs only, this is equally applicable to a sequential data set, a PDS, or a VSAM data. The MGMTCLAS parameter provides the management class to be used for a sequential data set, a PDS, or a VSAM data set that you are creating. And yes given an individual GDG, it has all the qualities of an QSAM.

Quote:
Then on 4th day will the fourth generation will be created since the limit is 3? and if it happens what will happen to the first version of the GDG, the retention period of which is not met on 4th day.
This is not the concept on which GDGs were build up, they say, if limit is "3" then at a given instant there will be 3-different generations (Expat sir, I recall something.. icon_smile.gif ) in the catalog, if on "4th" day a new generation forces to come in existance the most old GDG has "to die little younger"; alas, they are GDGs..& here retention period is not the enemy. Instead if 4th generation will be created on 11th day then very first GDG would be found "migrated"; this migration is because the retention period limit of "10 days".
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gcicchet

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Joined: 28 Jul 2006
Posts: 1703
Location: Australia

PostPosted: Tue Jul 22, 2008 4:26 pm    Post subject:
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Hi,

usually GDG's are rolled off when the max limit has been reached and the expiry date has not passed, the job creating the new GDG will normally throw up a message of the GDG that was not able to be scratched.

As far as the GDG would be found to be migrated is up to the MGMTCLAS and nothing to do with the retention period.

Gerry
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