In order to manage peer-to-peer remote copy (PPRC) operations,
you need to know the state of PPRC volumes. Figure 1 shows
the different volume states possible with PPRC. There are additional
states, SUSPEND.PM and SUSPEND.CG, not included
in the illustration.
Figure 1. PPRC volume states
To determine the state of a volume, issue the CQUERY command to
that volume. Querying PPRC volumes describes an example
of the command and the returned result.
The possible states for a volume are:
- SIMPLEX
- PENDING
- PENDING.XD
- DUPLEX
- SUSPENDED
- SUSP(n).XD
- SUSPEND.CG
- SUSPEND.PM
- MTIR
- UNKNOWN
The states that apply to volumes in cascading PPRC relationships are identified as follows:
- SIMPLEX.CAS
- PNDING.CAS
- PNDING.X.C
- DUPLEX.CAS
- SUSP.CAS
- SUSP(n).CAS
- SUS(n).X.C
The following definitions apply to volume states:
- SIMPLEX
- The
initial state of a volume.
- PENDING
- The
initial state of a defined volume pair. This state can also occur
after a storage subsystem failure when PPRC reestablishes the volume
pair. PPRC is in the process of copying data from the primary volume
to the secondary volume.
- PENDING.XD
- The state of a volume pair established in PPRC extended distance
while the copy operation is in process.
- DUPLEX
- The
state of a volume pair after PPRC has completed the copy operation,
and the volume pair is in synchronization.
- MTIR
- The state of a volume in a Multi-Target
Internal Relationship (MTIR pair). This is an internal relationship that is created between two
multi-target secondary volumes when the Multi-Target Mirror
environment is established (when multiple secondaries are created using the PPRC establish command).
It is also known as the Multi-Target Incremental Resync relationship.
If multi-target PPRC is
disabled in PARMLIB, the state is UNKNOWN rather than MTIR.
- Cascading States
- The
state of two volume pairs established through another application
(for example, ICKDSF or ESS Specialist) such that the secondary of
one pair is the primary of another pair.
- SUSPENDED
- The
state of a volume pair when the storage subsystems cannot keep the
primary and secondary volumes synchronized, or when either the primary
host or recovery site host issues a CSUSPEND command. A PPRC volume
pair will go into suspended state, for instance, when the primary
system storage control fails to complete a write operation to the
recovery system storage control. During this suspended state, the
primary volume’s storage control records the cylinders that applications
update. When you issue a CESTPAIR command with the RESYNC parameter,
PPRC must only recopy data in the cylinders that have changes. Both
volumes return to a synchronized state.
- SUSP(n). XD
- The state of a volume pair established in PPRC extended distance
and in suspended state.
- SUSPEND.CG
- The PPRC pair was suspended
as a result of a request to pause the Global Mirror session with consistency.
- SUSPEND.PM
- The
state of a volume pair when a FlashCopy® Establish
with Preserve Mirror Required was requested and the inband FlashCopy Establish sent from
the local control unit failed, resulting in the Local B to Remote
B PPRC pair being suspended. Local B and Remote B are FlashCopy targets. For more information,
see Preserving mirroring.
- UNKNOWN
- The state of a volume in a Multi-Target
Internal Relationship (MTIR pair) if multi-target PPRC is disabled in PARMLIB, or the CQUERY is
issued with UNFORMAT parameter.