On Tue, 23 May 2017 12:27:10 -0400, Tony Harminc ([email protected])
wrote about "Re: RACF Database (was: Sample JCL for file transfer using
NJE/TCPIP)" (in
<CAArMM9TiwTq=Wzf=hg1mj8zdsmx_ngyfg6xb+kpt3umpebm...@mail.gmail.com>):
On 22 May 2017 at 12:57, Paul Gilmartin <
[email protected]> wrote:
[snip]
How does ACF2, based on VSAM, meet this requirement of early availability?
The same way it would if ACF2 used BDAM or QSAM or... VSAM is not like VTAM
or TCP/IP or z/OS UNIX filesystems. There is no "VSAM address space" to be
initialized at some point in the IPL.* VSAM is almost entirely a
collection of subroutines, just like the older access methods.
* These days there are all sorts of "helper" address spaces around - VLF,
LLA, CATALOG, ... and I suppose one of those may need to be active in order
to allocate and open a VSAM dataset. But just to do the I/O, I don't think
so.
The CATALOG address space needs to be active just to open a VSAM
cluster. But CATALOG starts very early on in the IPL because it is
needed to access all and any of the pagespaces. This is because a
pagespace is a VSAM cluster too.
--
Regards,
Dave [RLU #314465]
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[email protected] (David W Noon)
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