On Feb 14, 2018, at 9:47 AM, R.S. <r.skoru...@bremultibank.com.pl> wrote:
> 1. KEY
> Nowadays there are two "datasets" using hardware key: VTOC and PDS directory.
> What about other files? Is it possible to allocate new dataset with hardware 
> key?
> According to JCL Reference, KEYLEN keyword can  be used for VSAM KSDS or for 
> non-SMS datasets including BDAM, SAM, BPAM, QISAM (!) and EXCP datasets.
> Is it still supported or just documentation is out of date?

My understanding is that the KEYLEN for a VSAM KSDS doesn’t refer the the CKD 
hardware key.

But why does it matter? Hardware keys are one of those “it seemed like a good 
idea at the time” things that didn’t pan out. CKD hardware keys are extremely 
slow and inefficient; you really don’t want to use them. IBM added the VTOC 
index to avoid using the hardware key when searching the VTOC, and PDSE to get 
away from the hardware keys in the PDS directory. Our lives would all be 
simpler and better if we could actually eliminate hardware keys.

> As far as I know, the PDS directory consist of 256-byte blocks, but the 
> 8-byte key is not part of the block. Is it correct?
> Or maybe it is 256 bytes including some 8-byte field which is repeated in Key 
> area?

The hardware key for a PDS directory block contains the name of the last member 
whose entry is contained in that block. The 256 bytes is the data portion of 
the block and does not include the 8 bytes of the key.

Pew, Curtis G
ITS Systems/Core/Administrative Services

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