TOD
Clock
Processing
The
CPC
TOD
clocks
of
all
the
CPs
are
automatically
set
during
CPC
activation.
The
time
reference
used
depends
on
whether
or
not
a
Sysplex
Timer
®
is
attached
to
the
CPC
or
Server
Time
Protocol
(STP)
is
enabled.
When
STP
is
enabled,
a
CPC
can
participate
in:
an
ETR
network,
a
Mixed
Coordinated
Timing
Network
(CTN),
or
an
STP-only
CTN.
In
an
ETR
network
or
Mixed
CTN,
the
Sysplex
Timer
provides
the
timekeeping
information.
In
an
STP-only
CTN,
the
Sysplex
Timer
is
no
longer
required.
In
this
case
the
Current
Time
Server
for
the
STP-only
CTN
provides
the
time
information.
No
Sysplex
Timer
Attached
and
Server
Time
Protocol
Not
Enabled
During
PR/SM
initialization,
the
CPC
TOD
clocks
for
each
CP
are
set
to
the
TOD
value
of
the
support
element.
Each
LP
starts
out
with
this
CPC
TOD
value
at
the
completion
of
LP
activation.
The
operating
system
running
in
an
LP
can
set
a
TOD
value
for
itself
and
this
will
be
the
only
TOD
reference
it
will
see.
Setting
the
TOD
clock
for
one
logical
CP
in
the
LP
sets
the
TOD
clock
for
all
logical
CPs
in
that
LP,
but
does
not
affect
the
logical
CPs
in
any
other
LP.
The
TOD
clock
value
is
used
for
the
duration
of
the
LP
activation,
or
until
a
subsequent
Set
Clock
instruction
is
issued
in
the
LP.
Sysplex
Timer
Attached
The
attachment
and
use
of
an
IBM
Sysplex
Timer
is
supported.
Also,
during
PR/SM
initialization,
when
a
Sysplex
Timer
is
attached,
the
CPC
TOD
clocks
for
each
CP
are
set
to
the
TOD
value
from
the
Sysplex
Timer.
The
operating
system
in
each
LP
can
independently
choose
whether
or
not
to
synchronize
to
the
Sysplex
timer
if
one
is
present.
Operating
systems
in
LPs
that
do
synchronize
to
the
Sysplex
Timer
will
all
be
running
with
identical
TOD
values.
Operating
systems
in
LPs
that
do
not
synchronize
to
the
Sysplex
Timer
do
not
need
to
be
aware
of
the
presence
of
a
Sysplex
Timer
and
can
set
their
TOD
values
independently
of
all
other
LPs.
Note
that
z/OS
does
not
allow
you
to
change
the
value
of
the
TOD
setting
when
it
is
using
the
Sysplex
Timer
(ETRMODE=YES
in
the
CLOCKxx
parmlib
member).
The
System
z9
models
support
the
specification
of
a
logical
partition
time
offset.
When
all
members
of
a
sysplex
are
in
logical
partitions
on
these
supported
models,
the
Logical
partition
time
offset
can
be
used
for:
v
Different
local
time
zone
support
in
multiple
sysplexes
using
the
same
sysplex
timer.
Many
sysplexes
have
the
requirement
to
run
with
a
LOCAL=GMT
setting
in
a
sysplex
(ETRMODE=YES)
where
the
time
returned
from
a
Store
Clock
instruction
yields
local
time.
To
do
this,
the
time
returned
by
the
sysplex
timer
must
be
local
time.
Prior
to
Logical
partition
time
offset
support,
this
could
only
be
accomplished
for
one
sysplex
for
a
given
sysplex
timer.
With
Logical
partition
time
offset
support,
multiple
sysplexes
can
each
have
their
own
local
time
reported
to
them
from
the
sysplex
timer
if
desired.
For
instance,
the
sysplex
timer
can
be
set
to
GMT,
one
set
of
sysplex
partitions
could
specify
a
Logical
partition
time
offset
of
minus
5
hours,
and
a
second
set
of
sysplex
partitions
could
specify
a
Logical
partition
time
offset
of
minus
6
hours.
Server
Time
Protocol
Enabled
The
enablement
of
STP
is
supported.
Also,
during
PR/SM
initialization,
when
STP
is
enabled,
the
CPC
TOD
clocks
for
each
CP
are
set
to
the
TOD
value
from
STP.
Chapter
1.
Introduction
to
Logical
Partitions
1-25
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