Hitachi VSP F1500 User And Reference Manual page 269

(1) Delivering the timestamp (CTQ-Marker)
CCI (HORCM daemon process) makes a table for the groups registered to the
horcm.conf as HORCM_CTQM with startup, and makes the threads for each
group that delivers the same timestamp with an increment to the multiple
storage systems configured in a group. The thread for a group delivers the
same timestamp with increments, as far as a group configured Universal
Replicator in the PAIR status.
The timestamp is delivered by using Freeze/Q-Marker & Run way as default.
The timestamp is maintained in each storage system. CCI includes this
timestamp with startup, and then delivers the same timestamp with
increments to each storage system.
(2) Arbitrating/committing the journal data with CTQ-Marker
The thread for a group on HORCM compares the timestamp of S-JNL on each
storage system (RCU) as far as a group configured Universal Replicator in
PAIR state. Once HORCM detects a matching point of the timestamp (CTQ-
Marker) on all storage systems (RCU), it issues an order to commit the
Journal data with CTQ-Marker to each storage system (RCU).
(3) Propagating Error suspend
The thread for a group on HORCM delivers the same timestamp with
increments as far as a group configured Universal Replicator in PAIR state. If
the PSUE/PFUS state detects at least one storage system, then it notifies
another storage system to suspend PSUS in order to keep the state
consistent in the consistency group. Then the thread stops to deliver the
timestamp, and keeps monitoring its consistency group with interval of
HORCM_CTQM until it becomes PAIR state by next pair-resync.
(4) Committing the Journal data inside pairsplit command
The pairsplit command makes a suspending state on PAIR state, and inherits
to compare the timestamp of S-JNL on each storage system (RCU). If it
detects a matching point of the timestamp (CTQ-Marker) on all storage
systems (RCUs), then it issues an order to commit the Journal data with Q-
Marker to each storage system (RCU), and repeats it until it detects an EOM
(End Of Marker) of CTQ-Marker with the pairsplit command.
horcm.conf
CCI supports TC_Sync group across multiple storage systems, but it does not
allow TrueCopy Async (UR) group across multiple storage systems. Therefore,
CCI needs to add the group definition (HORCM_CTQM) in order to allow
making TrueCopy Async(UR) group across multiple storage systems. Then the
HORCM daemon process delivers the timestamps (called the consistency Q-
Marker), and commits S-VOL Journal data with Q-Marker to the defined
group.
6-45
Data replication operations with CCI
Command Control Interface User and Reference Guide