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Use of Enqueue datasets while accessing IMS when IRLM=N

 
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Amit.Agarwal

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Joined: 09 Feb 2013
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PostPosted: Tue Mar 19, 2013 4:02 pm    Post subject: Use of Enqueue datasets while accessing IMS when IRLM=N
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Hi!

I am analyzing possible changes required in batch processes when we convert IRLM=N to IRLM=Y? Can someone broadly list down possible changes that may be required in batch(for e.g. PROCOPT to be reviewed, Enqueue datasets etc.)

Also, specific to Enqueue datasets, can someone also explain the significance of usage of Enqueue datasets while accessing IMS DB when IRLM = N?
And when IRLM=Y, for which PROCOPTs, would enqueue datasets be required and for which scenarios, can we omit the usage of enqueue datasets?
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Anuj Dhawan

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PostPosted: Tue Mar 19, 2013 5:17 pm    Post subject:
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You're asking a tricky thing and I think you should get involved with your IMS DBA. OTOH, this might help a bit:
Quote:
To define the default IRLM support specifications for batch systems in a data-sharing environment, use the IRLM= keyword on the IMSCTRL macro. You can override specifications made in the IMSCTRL macro by using the IRLM= keyword in the batch JCL.

In batch systems, you can specify IRLM=Y or IRLM=N. If you specify IRLM=N:

•IRLM does not perform locking for the batch system.
•The batch system cannot participate in block-level sharing.
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Amit.Agarwal

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PostPosted: Wed Mar 20, 2013 12:56 pm    Post subject:
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Anuj, my requirement is to find modifications that would be required from application programming point of view. The link does not provide the necessary information. As you said, I am already in connect with our DBA but would have been helpful if I would have got few insights from the forum.
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PeterHolland

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PostPosted: Wed Mar 20, 2013 1:09 pm    Post subject:
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The following link may provide you with some answers :

http://proceedings.share.org/client_files/SHARE_in_Anaheim_2/Session_8566_handout_578_0.pdf
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Anuj Dhawan

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PostPosted: Wed Mar 20, 2013 2:56 pm    Post subject:
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You also had
Quote:
specific to Enqueue datasets, can someone also explain the significance of usage of Enqueue datasets while accessing IMS DB when IRLM = N?
in your question - which is explained in that link, so that's not exact link for all the questions you might have but a bit of direction.
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Gary Jacek

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PostPosted: Thu Mar 21, 2013 2:51 am    Post subject: Re: Use of Enqueue datasets while accessing IMS when IRLM=N
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Hi Amit

It seems strange that you mention Enqueue datasets.

IRLM=N implies you are using PI locking.
IRLM=Y takes you to IRLM locking.

In both cases, IMS manages the locks and you don't need Enqueue datasets, UNLESS...

You have coded database dataset dispposition/VSAM Share Options that permit other batch jobs to access your database datasets at the same time IMS has them.

Or you periodically take your databases offline from the IMS Control Region and you have a free-for-all gaggle of DLI batch jobs running against them, using Enqueue datasets to single thread them.

If this is the root of your Enqueue question, you should read "DBRC In Practice" by Peter Armstrong, available for free, from your nearest BMC Software representative. Peter explains at some length as to why you should not be running DLI batch and why you should also have all of your production databases registered in DBRC.

There is some cost associated with converting from PI to IRLM locking.
If you are doing this to get to data sharing, you really need to have all your DBRC work done and hopefully your DLI batch converted to BMPs.

Sorry, I got up on my soap box. I hope some of this is of value to you.

Gary

Amit.Agarwal wrote:
Hi!

I am analyzing possible changes required in batch processes when we convert IRLM=N to IRLM=Y? Can someone broadly list down possible changes that may be required in batch(for e.g. PROCOPT to be reviewed, Enqueue datasets etc.)

Also, specific to Enqueue datasets, can someone also explain the significance of usage of Enqueue datasets while accessing IMS DB when IRLM = N?
And when IRLM=Y, for which PROCOPTs, would enqueue datasets be required and for which scenarios, can we omit the usage of enqueue datasets?
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Amit.Agarwal

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Joined: 09 Feb 2013
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PostPosted: Thu Mar 21, 2013 2:58 pm    Post subject:
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Thanks Gary, your inputs are in-line with the path I have been trying to take.So, will elaborate a bit further on this.

The idea we are trying to conceptualize is, If there is a possibility to keep the onlines up while batch cycle is running - in a nutshell!

So we intend to look into the possibility, to modify all of our batch cycle / DLI jobs that do not use IRLM, to start using IRLM=Y.
(and because many of batch processes could use same IMS databases concurrently that is why trying to explore if usage of enqueue is required when IRLM=Y also, to serialize the accesses to a database).

You are correct, the idea is to achieve data sharing, between Onlines & Batch, we had suggested conversion to BMPs, but our DBAs have suggested IRLM=Y, a more feasible approach to pick of the two.
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Amit.Agarwal

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PostPosted: Fri Mar 22, 2013 3:27 pm    Post subject:
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Gary, as I can understand from your statement above, will the following be true then ? -

1) To keep the data sharing going on between Online Screens while Batch is running, we would need to keep databases up for the IMS Control Region, while the batch jobs run with IRLM='Y'???

2) Enqueue datasets will not be required now because updates can be managed by IRLM locking? Or would we still need enqueue datasets in cases when for e.g. there are multiple DLI Batch jobs accessing a particular database, or Screen is accessing a database while a batch job updates the same.
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