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A real time VSAM scenario

 
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Gaurav Chauhan

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Joined: 29 Oct 2007
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PostPosted: Tue Nov 02, 2010 11:30 am    Post subject: A real time VSAM scenario
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A customer has a KSDS file loaded with just one record with key value 0.
He runs a batch job to add a few records with very high numeric key.
He has an online application which is capable of adding lots of records which can have keys less than the ones inputted by batch.

Will the application create any problem?

If yes, what is the problem and its solution?

Thanks & regards
Gaurav Chauhan.
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expat

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PostPosted: Tue Nov 02, 2010 3:14 pm    Post subject:
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What has happened so far. Are there any problems.
Have you monitored the KSDS file, and if so what did you see in the way of changes or whatever.

This is something that you should investigate for yourself and then post if you find problems or something you do not understand.
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Robert Sample

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PostPosted: Tue Nov 02, 2010 4:12 pm    Post subject:
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Doing simultaneous updates in batch and online to a VSAM file has been discussed in the last week on this forum. Have you searched the forum yet?
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expat

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PostPosted: Tue Nov 02, 2010 4:15 pm    Post subject:
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Robert Sample wrote:
Have you searched the forum yet?
36_11_6.gif
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Robert Sample

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PostPosted: Tue Nov 02, 2010 4:17 pm    Post subject:
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Hey, expat, one can hope, right? icon_biggrin.gif
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expat

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PostPosted: Tue Nov 02, 2010 4:41 pm    Post subject:
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Yeah. I do, along with others, try to steer the posters to the correct route to follow for problem resolution, but some days I just give up.

Guess today could be one of my more acidic days icon_lol.gif
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Robert Sample

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PostPosted: Tue Nov 02, 2010 5:09 pm    Post subject:
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Well, let's answer the original questions:
Quote:
Will the application create any problem?

If yes, what is the problem and its solution?
Yes, the application will create problems. These problems can vary from not being able to access recently added records to complete file corruption requiring the VSAM file to be deleted and rebuilt from scratch.

There is a link to manuals at the top of the page. Click on it, find the manual titled "VSAM Services for DFSMS" (which IBM calls DFSMS Access Method Services for Catalogs) and read -- extremely carefully -- the DEFINE CLUSTER options for SHROPTIONS. Updating a VSAM file online and in batch at the same time can be done -- but it requires use of enqueue and dequeue to serialize the updates. If updates are not serialized, the index and data components can get out of sync and if that happens the VSAM file must be deleted and rebuilt.
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expat

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PostPosted: Tue Nov 02, 2010 5:34 pm    Post subject:
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Robert,

I was thinking along the same lines and would have suggested an investigation into DFSMStvs as an option.

However, and not at all surprising, the OP had given insufficient information for me to want to comment as they did not specify concurrent updates, so I assumed sequential update of the file, first by batch and subsequently via oline transaction(s).

As more experienced users we should be aware of possible pitfalls but wouldn't it be oohhh soooooo nice to actually have someone post on the forum and give ALL of the information in the first post.

Guess that's about the same probability of winning the lottery really.
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Robert Sample

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PostPosted: Tue Nov 02, 2010 5:55 pm    Post subject:
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I think the lottery odds are somewhat better -- the two big games here are 139 million to 1 and 195 million to 1!

Even without simultaneous updates online and in batch, there's a real potential for data corruption -- if the online application just inserts records after the batch updates are done, I can still see issues unless the online system closes and reopens the file (and what a waste that could be)!
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dick scherrer

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PostPosted: Tue Nov 02, 2010 9:01 pm    Post subject: Reply to: A real time VSAM scenario
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Quote:
wouldn't it be oohhh soooooo nice to actually have someone post on the forum and give ALL of the information in the first post
Methinks that the folks who know "all of the information" also know the pitfalls/problems. . .

I believe we're here primarily for the folks who don't have so much depth yet. . . icon_cool.gif

d
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Akatsukami

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PostPosted: Wed Nov 03, 2010 1:15 am    Post subject:
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expat wrote:
wouldn't it be oohhh soooooo nice to actually have someone post on the forum and give ALL of the information in the first post.

If it's any consolation, I spent a non-trivial proportion of my time dealing with defect reports from my own shop (I'm the senior tools development analyst, therefore I must know everything, right? Be nice if it were true...) showing the same appalling misunderstandings and lack of useful information. The only difference is that I'm close enough to the querents to limp over to them and beat them with my cane until they tell me what I need to know to solve their problems.
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