Maybe it's illusory, but that is in David Raften document.
Obviously it's cheaper to have 2 CPCs than 3, but it is also cheaper to
have 1 CPC than 2.
The white paper clearly describes some structures as demanding duplexing
or third CPC with failure-isolated CF.
--
Radoslaw Skorupka
Lodz, Poland
W dniu 2018-07-11 o 01:15, Jesse 1 Robinson pisze:
It's easy to diss a solution as 'budget' when it saves someone *else* money.
The notion that a third CEC for standalone CF is substantially better than ICF
is illusory. If you truly believe that one extra CEC is necessary, then you
really need two extra CECs for CF because there are times when you have to take
one of them down. Maybe for repair, maybe for upgrade. So you still need a
backup.
OTOH, 'logical standalone'--interesting term--with an ICF in each z/OS CEC is a
sufficient solution. We've run this way for years and survived two separate
hard-down CEC failures with zero recovery agony. My recommendation is to run
two CECs, one substantial box to run application hosts, and a minimal 'penalty
box' just for ICFs plus a few high-cost products that bill significantly less
on a small CEC. With proper structure duplexing, you have extraordinary
redundancy at a reasonable cost.
.
.
J.O.Skip Robinson
Southern California Edison Company
Electric Dragon Team Paddler
SHARE MVS Program Co-Manager
323-715-0595 Mobile
626-543-6132 Office ⇐=== NEW
robin...@sce.com
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf
Of R.S.
Sent: Tuesday, July 10, 2018 3:00 AM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: (External):Re: Sysplex between two hardware
W dniu 2018-07-10 o 06:56, Timothy Sipples pisze:
I should also respond to this part:
Radoslaw Skorupka wrote:
...for availability reasons one should avoid having CF and z/OS LPAR
on the same hardware, which means....
That's not phrased as IBM would phase it, and it's not correct as written.
Even when there's some merit in physically separating the CF, the
physical separation need only be between that CF and the particular
z/OS Parallel Sysplex it serves. Having other z/OS LPARs, even LPARs
that are participating in other Parallel Sysplexes, on the same
machine as the CF is consistent with IBM's recommendations here.
David Raften has published a whitepaper (updated in May, 2018) that
explains the various CF configuration options. The direct link to the
current edition is here:
https://public.dhe.ibm.com/common/ssi/ecm/zs/en/zsw01971usen/zsw01971u
sen-.pdf
[...]
I quickly browsed the document and found confirmation what I learned several
years ago.
That means:
Yes, you need either standalone CF (*see note) or CF structure duplexing! This
is required for *some* structures, but ...it is. David Rften call it structures
which /require failure independence/.
Note: Standalone CF should be understood here as LOGICAL stand alone CF.
IBM-MIAN do not allo pictures, so I'll try to describe it:
SYSPLEX PROD:
z/OS 1 in CPC A, z/OS 2 in CPC B, and CF2 in CPC B or A. And CF1 in CPC C.
Three CPCs.
However CPC C may be used for other purpose, i.e. for test LPARs.
Anything but z/OS image belonging to the sysplex PROD.
There is also two-CPC configuration
z/OS 1 + CF1 in CPC A, z/OS 2 + CF2 in CPC B and *some structures are duplexed*.
What I heard unofficially from IBM-ers is such configuration is "budget"
read: when you cannot afford good one.
And the link between CFs should be really local (short).
Note2: it is also possible to build a configuration without dedicated
(logical stand alone) CF and without duplexing. Your choice.
However it is NOT resistant to all possible (single) failures. Yes, it
is still better than parallel sysplex with single CF, but still
vulnerable to some failures.
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