HP XP for Compatible Extended Remote Copy Software Licenses - Manual (Page 14)

is not performed due to the failure. However, the write order (sequence) is maintained so that the
write process can be re-initiated after recovery.
A session is further divided into internal sessions called storage control sessions (SC sessions) per
each volume. SDM reads the data written to the 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 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
Note: For details of the TSO commands in Compatible XRC, see DFSMS Advanced Copy Services
(Document number: SC35-0428-02) published by IBM.
Configuration
HP Compatible XRC operations require hosts and XP24000/XP20000 Disk Array storage systems at
the primary site; should operation at the secondary site be required, a secondary storage system (or
storage system) must have the capability 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 SDM, which is host
software, for remote copy operations. The XRC program product needs to be installed in the primary
storage system. The primary site requires a XP Remote Web Console PC for setting XRC program
product options.
Figure 2 on page 15 shows the connection configuration of channel extenders for Compatible XRC.
Notice that LCP/RCP configurations can be either ESCON or FICON.
About Compatible XRC Operations 14