HP XP P9500 Storage - Manual (Page 6)

is not performed due to the failure. However, the write order (sequence) is maintained so that the
write process can be reinitiated after recovery.
A session is further divided into internal sessions called storage control (SC) sessions per each
volume. SDM reads the data written to the P9500 storage system at the primary site in order of
time stamp in each SC session. SDM checks the time stamp of each SC session, and determines
in what order the data is written to the secondary volumes. Data is written to the secondary volumes
in units of session in the same order as it was written at the primary site, not in units of SC session.
SDM manages definitions of sessions and SC sessions.They are defined for session IDs and volumes
by TSO command in the storage system.
TSO commands
The following settings concerning XRC operations are defined by the Time Sharing Option (TSO)
commands issued to the storage system from the host system.
•
Creation and deletion of pair volumes
•
Creation of utility volumes
•
Display of pair status
•
Display of session status
•
Display of utility volume status
•
Integration and withdrawal from the session
•
Recovery at the secondary site
•
Resuming suspended pairs
•
Start and end of the session
•
Suspending of pairs
For details on the TSO commands for Compatible XRC operations, see the IBM document DFSMS
Advanced Copy Services (SC35-0428-18).
NOTE: The last two digits of the IBM document number indicate the version. Version 18 is the
version of the Advanced Copy Services document for z/OS 1.12.
Configuration
Compatible XRC operations require hosts and storage systems at the primary and secondary sites.
If operation at the secondary site is required, the secondary storage system (or systems) must be
capable of supporting the XRC workload. If the system at the primary site consists of several hosts,
a SYSPLEX timer is required in the primary host to provide a common time reference for the I/O
time-stamping function. The secondary host requires the SDM host software for remote copy
operations. The Compatible XRC feature needs to be installed in the primary storage system, and
the Remote Web Console is required at the primary site for setting XRC options.
The following shows the connection configuration of channel extenders for Compatible XRC
operations.
6 Overview of Compatible XRC