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2-26 Chapter 3 Preparing for Universal Replicator z/OS Operations
Hitachi Universal Replicator for IBM /OS User’s Guide
Note: The primary storage system does not remove the target journal data from
its master journal volume until it receives the sequence numbers of restored
journal which is give to the read journal command from the secondary storage
system. This is true even if the primary storage system and secondary storage
system are connected via a channel extender product.
Selecting and Restoring Journal at the Secondary Storage System
The secondary storage system selects journal data to be promoted to formal
data (or " restored") as follows:
1. The secondary storage system gives the number as the management
information to distinguish the journal data arrival to the sequence number
that is assigned to the journal data from the primary storage system. If the
number is 1, the journal data arrived at the secondary storage system. If
the number is 0, the journal data has not arrived yet. The secondary
storage system determines whether the journal data should be settled or
not according to this number. If the journal data has not arrived yet, the
secondary storage system waits for the journal data.
2. When the top of queue in the journal group indicates the journal data
arrival, the secondary storage system selects the journal data which has
the lowest sequence number, and then settles this journal data.
3. The secondary storage system repeats steps (1) and (2) to select and
settle the journal data.