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2-24 Chapter 3 Preparing for Universal Replicator z/OS Operations
Hitachi Universal Replicator for IBM /OS User’s Guide
Note: The number of bitmap areas affects the maximum possible number of
pairs that can be created in the storage system. For details on the maximum
possible number of pairs, see section
The Maximum Number of Pairs.
Journal Processing
The URz journal data contains the primary data volume updates and the
metadata information (associated control information), which enables the
secondary storage system to maintain update consistency of the URz
secondary data volumes. URz journal processing includes:
• Creating and storing journals at the primary storage system (see the next
section),
• Copying journals to the secondary storage system
• Storing journals at the secondary storage system
• Selecting and restoring journals at the secondary storage system
• Types of journals
Journal Processing at the Primary Storage System
When a primary storage system performs an update (host-requested write
I/O) on a URz primary data volume, the primary storage system creates a
journal data to be transferred to secondary storage system. The journal data
will be stored into the cache at first, and then into the journal volume.
Metadata information will be attached to journal data (see
Table 2-3). When
base-journal is obtained, only metadata information is created and stored in
UR cache or the journal volume.
Table 2-3 Metadata Information
Type Description
Journal type Type of journal (e.g., base-journal or update journal)
LDEV No. (data) The number of primary data volume that stores the original data
Original data storing position
The primary data volume slot number, and the start and end of sub-block
number (data length)
LDEV No. (journal) The volume number of master journal volume that stores the journal data
Journal data storing position The slot number of master journal volume, and the start sub-block number
Journal sequence number The sequence number that is assigned when the journal is obtained
Timestamp The time when the journal data is obtained