DSCB Model (JCL) 1

[121854]

I need to define or set DSCB model for a dataset. Could someone let me know where could I find information that enable me to define and catalog the DSCB model for a GDG dataset.

Your assistance and guidance will be appreciated.

Luis

 

[slade]

Hi Luis,

As I recall:

A model DSCB is required when creating tape GDGs. Since disk resident GDGs have, by definition, their own DSCBs, a "model" is not required. At one time tape GDGs needed disk resident DCB info to work properly. With the advent of SMS, this may not be required.

It is just a disk resident dataset (usually with zero space allocated). The most popular way to allocate one is via IEFBR14, but they can be created using any method that one would use to allocate a QSAM disk dataset.

They are called "Model DSCBs" because you can create only one and use it for every GDG your shop creates. If the GDG you're creating has the same DCB attributes as the model, you need only specify "DCB=yourmodeldscbname". If they're different, you override the model DCB attributes, e.g.
DCB=(yourmodeldscbname,LRECL=222,BLKSIZE=2000,RECFM=VB).

Your shop probably already has one (or more). You might want to ask your tech guys. If not, see below.

THE ALLOCATE STEP WOULD LOOK SOMETHING LIKE THIS:

//S1 EXEC PGM=IEFBR14
//MDSCB DD DSN=PROD.MDSCB,DISP=(,CATLG,CATLG),
// UNIT=DISK,SPACE=(TRK,(0)),
// DCB=(RECFM=FB,LRECL=80,BLKSIZE=0)

Use the attributes of the most popular dataset size for your shop to reduce the need for DCB overrides.

HTH, Jack.

 

[slade]

A correction to my previous post. I found some info in an IBM manual that states that the model DSCB must be allocated on the catalog volume, so that means that a model DSCB is required by ALL GDGs, not just tape GDGs.

Sorry about that, Jack.