IBM System storage DS6000 Series, Redbook

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142
IBM System Storage DS6000 Series: Copy Services with IBM System z
The volume pair is suspended and further writes to the source volume are not accepted if
data cannot be sent to the target volume.
13.3.5 Consistency Group and critical mode combination
Table 13-1 shows what happens when the CRIT parameter of the CESTPAIR command, and
the CGROUP parameter of CESTPATH command are combined. These options can also be
set using the DS CLI, or with the DS Storage Manager GUI.
Table 13-1 Interaction of CRIT and CGROUP parameters
The IEA494I message with SUSPENDED status is issued for the in-error pair to all z/OS images
that have the primary volume online. An IEA491E message is returned to the issuing system
of the next I/O that is attempted to the volume that is suspended. For open systems, an
SNMP trap will be issued to the address specified when the DS6000 SNMP service was
configured.
For further discussion on the CGROUP and the CRIT parameters, refer to z/OS DFSMS
Advanced Copy Services, SC35-0428.
13.4 Metro Mirror paths and links
Metro Mirror pairs are set up between volumes in LSSs, usually in different disk subsystems,
and these are normally in separate locations. A
path
(or group of paths) needs to be defined
between the primary (source) LSS and the secondary (target) LSS. These
logical paths
are
defined over
physical links
between the disk subsystems.
The physical link includes the host adapter in the primary DS6000, the cabling, switches or
directors, any wideband or long distance transport devices (DWDM, channel extenders,
WAN), and the host adapters in the secondary disk subsystem. Physical links can carry
multiple Metro Mirror logical paths, as shown in Figure 13-5 on page 143.
CRIT(Y) CRIT(N)
CGROUP(Y) IEA494I with long busy state
(SNMP trap for open systems) IEA494I with long busy state
(SNMP trap for open systems)
Pair in error suspended Pair in error suspended
Unit check on primary device No unit check on primary device
IEA494I when suspended IEA494I when suspended
CGROUP(N) No long busy state No long busy state
Pair in error suspended Pair in error suspended
Unit check on primary device No unit check on primary device
IEA494I when suspended IEA494I when suspended
Note: For Metro Mirror, the DS6000 supports Fibre Channel links only. To facilitate ease of
testing, the DS6000 does support Metro Mirror source and target on the same DS6000.