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Chapter 2 About Universal Replicator Operations 2-27
Hitachi Universal Replicator for IBM /OS User’s Guide
Figure 2-6 illustrates the journal data selection and settling at the secondary
storage system. This diagram shows that journal data S1 arrives at the
secondary storage system because the management information indicates 1.
The secondary storage system selects journal data S1 to be settled, because
S1 is the lowest sequence number. When S1 is removed from the queue of
sequence numbers, journal data S2 becomes the top entry, but it has not
arrived yet. The management information of journal data S2 is 0. The
secondary storage system waits journal data S2. When journal data S2
arrives, the secondary storage system selects S2 as the next journal data to
be settled. The journal data selected by the secondary storage system is
marked as “host-dirty” and treated as formal data.
S1 to S4: Sequence number
(1): The journal data arrived.
(0): The journal data has not arrived yet.
S1
Receiving
journal data
Selecting
journal data
Setting
journal data
Formal
j
ournal
data
Data
S4 (1) S3 (1)
S2 (0)
S1 (1)
Gr
p
=
n
Gr
p
=
n
Figure 2-6 Selecting and Settling Journal at the Secondary Storage
System
The secondary storage system settles and restores the journal data to the
secondary data volume as follows:
• Journal data stored in the cache
The journal data is copied to the corresponding cached track and promoted
to formal data.