change in LRECL of GDG's new generation.

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

hi folks,

I have created a new GDG base (GDG Limit = 100) and a model dataset with following DCB parameters DCB=(LRECL=80,RECFM=FB,DSORG=PS)

i have added 50 generations to the base by refering Model dateset DCB parameters so far. however due to requirement change, LRECL of Generation is changed to 90 but rest of DCB parameters are same.

Now if i try to add 51st generation (LRECL 90) to the base, it will error out saying 'CONFLICTING DCB PARAMETERS ' .

what i need, is to have 50 generations to be kept with old DCB and new 51st to be with LRECL 90.

we can do it by creating a new GDG with LRECL 90 and copy all 50 generation first and then add 51st generation.

but i am curious to know whether can we achieve thru any other method.
(Note: we dont have file-aid at present)

Thanks

expat · Posted: Fri Jul 12, 2013 2:14 pm

Don't know why you're even bothering using a model DSCB.

Using SMS, the model DSCB has not been required for about 20 years now.

Get rid of the model DSCB from any statements creating a new generation and see what happens.

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

I am unaware of "What is model DSCB"

. .

You mean to say, creating a generation using model dataset's DCB is called as "model DSCB".

please throw some light on how to get rid of this " model DSCB".

kindly provide some documents or any urls will do.

In the mean time let me go thru manuals.

expat · Posted: Fri Jul 12, 2013 2:59 pm

Show the JCL that you are using to try and create the new generation.

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

expat · Posted: Fri Jul 12, 2013 3:16 pm

What is model DSCB - perhaps a clue may be seen below

DCB=(MODLDSCB,RECFM=FB,LRECL=172,BLKSIZE=0)

Just code the RECFM & LRECL paramters for that line and see what happens.

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

Thanks for teaching perhaps out of curious i have a doubt here, if i remove this keyword MODLDSCB and if i execute the JCL with another LRECL value (eg: LRECL=200) for new generation.

will it give an error ?

expat · Posted: Fri Jul 12, 2013 3:20 pm

Why don't you try it and see

Nic Clouston · Posted: Fri Jul 12, 2013 3:20 pm

see the bit

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

Thanks Nic and expat for your suggestion.

Nic,
yes, DEPT.TEST.RPT is a very big file, having many sub reports within this file. its created using area sweep in IDMS (COBI ) module

Dale Robertson · New User Joined: 21 Jun 2013 Posts: 44 Location: U.S.A.

bvarun,

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

Thanks Guys for the support..

i removed MODEL DCB keyword and i can add variable LRECL generations to a GDG base.

dick scherrer · Posted: Mon Jul 15, 2013 8:04 pm

Hello,

Just be aware that if generations are created with different/conflicting dcb parameters, the files may cause a failure when some other process "knows" the wrong dcb info . . .

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

You mean DCB parameters like DSORG

Nic Clouston · Posted: Tue Jul 16, 2013 11:42 am

No - more like LRECL. If that changes from dataset to dataset then you, and your program, need to be aware of the fact and cater for it.

dick scherrer · Posted: Tue Jul 16, 2013 8:22 pm

Hello,

As Nic mentioned, a big vulnerability is changing lrecl. Blksize can be an issue if more than one generation is to be concatenated into a run.

Why does someone believe it is acceptable to catalog new generations with unlike dcb parameters?

I've asked some contacts and none of their organizations permit this. If the file is to be "different" a different DSN should be used rather than a new generation.

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

Thanks Dick for your inputs.

a Quick question here, can we see information about GDG base in ISPF

. Since we dont have File-aid in our shop, i tried in '3.4' option. but couldnt see it.

expat · Posted: Wed Jul 17, 2013 11:48 am

IDCAMS LISTCAT gets you everything you need to know about a GDG base

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

thanks Expat.

I am so happy to be part of this forum

.. You guys are very supportive

Pete Wilson · Posted: Tue Jul 23, 2013 1:16 pm

BV - a model DSCB is just a dataset created with 0 space and whatever LRECL,RECFM values etc. So it is just a DataSetControlBlock in the VTOC (Volume Table of Contents) on a DASD (Direct Access Storage Device) volume (or disk), but has no space allocated for the file.

It is still possible to use them but is unnecessary and not encouraged since ICF catalogs and SMS were introduced a few decades ago. All they do is provide 'model DCB allocation attributes' such as LRECL and RECFM etc for the dataset you're creating. If the dataset you're creating needs a change in LRECL then you'd have to redefine the MODEL DSCB if you're relying on that, and there could be numerous other things referring to that MODEL DSCB that DON'T want their attributes changed. So best to never use them these days.

The nearest DSCB equivalents now are the LIKE or REFDD JCL keywords which perform a 'similar' function by copying attributes of the file they're refer to to the new dataset you're creating, but they also provide SPACE and other attributes like SMS classes as well. You can also override individual values for your new dataset by specifying LRECL, SPACE or other keywords and it merges these together.

For SDB, it is usually best to use that as it will always to provide the nearest to half-track blocking factors which is more space efficient. If you don't understand blocking just don't code BLKSIZE. (There are a few exceptions to this but not many). I'd rather see users ommitting BLKSIZE or coding BLKSIZE=0 to get SDB than attempting to work out the correct BLKSIZE and messing it up. If you do a test allocation and load of LRECL=80,RECFM=FB file with a few thousand records and specify BLKSIZE=80, then try the same without specifying BLKSIZE, you will see the massive different in file size. The reason is every block has a 32 byte interblock gap which is effectively wasted space.

bvarun. · New User Joined: 05 Jul 2013 Posts: 34 Location: India

Thanks pete