You will need to know how many records, the average record length, and then if 
KSDS, just a DATA/INDEX or AIX or PATH

The VSAM Demystified Redbook is good for working with VSAM.

My thoughts are that the less splitting the better for the file.  But that 
means understanding how much free space, monitoring for CI/CA splits and the 
JCL used to access it.

Are you using AMP?  Are you using BUFNO, BUFNI, etc...


Lizette


> -----Original Message-----
> From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of
> Peter
> Sent: Wednesday, April 11, 2018 12:10 AM
> To: IBM-MAIN@LISTSERV.UA.EDU
> Subject: Re: Dummy question on VSAM multivolume
> 
> Hello Lizette
> 
> Thanks for the great explanation
> 
> I am trying to make the KSDS as multivolume using extended addressability
> above 4.2G. The KSDS tends to grow in our shop
> 
> So what would be your suggestion on the allocation for the above scenario.
> 
> How much should I go for the data and index ?
> 
> On Wed 11 Apr, 2018, 1:27 AM Lizette Koehler, <stars...@mindspring.com>
> wrote:
> 
> > - Ok This is one of my buttons
> >
> > PRI = 1000
> > SEC = 500
> >
> > The best practice in todays storage arena, is to allocate the small on
> > Primary and Large on Secondary
> >
> > Why - because the primary allocation can take away for the number of
> > secondary allocations that can be made
> >         Because the Primary allocation can only be obtained once and
> > upto
> > 5 extents to acquire it
> >
> > But using a small primary and large secondary you provide breathing
> > room for your dataset
> >
> > Also, you might want to calculate how much storage you might need and
> > determine the allocation needed from it
> >
> >
> > So for this file,  I would recommend, Primary = 100     Secondary = 1000.
> > Then monitor the file for growth.  If it looks like it is taking on
> > too many secondary extents, then reallocate and double or triple the
> > secondary
> >
> > If it is truly going to be over 4gb - then make the secondary huge
> >
> >
> >
> > Lizette
> >
> > > -----Original Message-----
> > > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On
> > Behalf Of
> > > Peter
> > > Sent: Tuesday, April 10, 2018 10:49 AM
> > > To: IBM-MAIN@LISTSERV.UA.EDU
> > > Subject: Dummy question on VSAM multivolume
> > >
> > > Hi
> > >
> > > I have defined a KSDS with primary 1000 and secondary 500 with the
> > extended
> > > addressability.
> > >
> > > It got created as multivolume with 2 volcount.
> > >
> > > Can I alter volume count ?
> > >
> > > Peter

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