What is MLDSCB?

[Binamra]

Hi ,

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// DCB=(MLDSCB,DSORG=PS,RECFM=FB, 
// LRECL=100,BLKSIZE=0) 

In above what is MLDSCB?

[Anuj Dhawan]

MLDSCB is "Model DCB".

Long aga, before you can create the files that attach to a GDG base, you need to create a model data-set that contains the DCB information for the files. This model data just needs to be a VTOC entry, it does not need to actually use up disk space. It is possible to create a different model data-set for every possible DCB combination, and some sites actually do that, but this needs a lot of effort to maintain. Many sites use a single model data-set, and then override the DCB information to build the correct type of file. To create a model DCB, use a dummy IEFBR14 job like this:

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//STEP2  EXEC PGM=IEFBR14 
//MODEL1 DD   DSN=THIS.IS.A.GDG.MODEL, 
//            DISP=(NEW,KEEP,DELETE), 
//            UNIT=SYSDA, 
//            SPACE(TRK,0), 
//            DCB=(LRECL=80,RECFM=FB)

The SPACE=(TRK,0) parameter means that this file will just be created as a VTOC entry, it will not use up disk space.

Said that, these DSCBs are no longer required if DFsms is installed and tailored correctly and most of the shops are "tailored correctly these days"!

[Binamra]

Thank You Anuj. What if SMS is not activated, then?

[Robert Sample]

If SMS is not active, then model DSCB data sets will be required for creating a GDG generation (for example).

[Binamra]

Thanks Robert.