Hitachi TrueCopy for z/OS (T1711-96009, June 2006)

TrueCopy for z/OS user guide 41
The MCU stores a cylinder bitmap in cache for each TC390A M-VOL and the RCU stores a cylinder bitmap
in cache for each TC390A R-VOL. When a TC390A pair is suspended, the cylinders that contain the
following records are marked in the cylinder bitmap as modified (to be copied during the resume pair
operation):
• The recordsets that were created by the MCU but not yet sent to the RCU. After marking these cylinders
as modified, the MCU discards these recordsets.
• The recordsets that were sent to the RCU but not acknowledged by the RCU. The MCU marks these
M-VOL cylinders as modified and discards these recordsets. This ensures that recordsets that are lost
during transmission to the RCU are identified and marked.
• The recordsets that reached the RCU but have not yet been settled. After marking these cylinders as
modified, the RCU discards these recordsets.
• The M-VOL records updated by host-requested write I/Os after the volume pair was suspended (same
function as for TC390 Synchronous pairs).
When a suspended TC390A pair is resumed (resynchronized), the contents of the RCU’s cylinder bitmap
are sent to the MCU and merged into the MCU’s cylinder bitmap. The MCU then performs the resync copy
operation according to the merged bitmap. This ensures that all cylinders containing recordsets that were
discarded are resynchronized at this time.
PPRC Support
An XP1024/XP128/XP12000/XP10000 with TC390 installed supports IBM PPRC host software functions.
You can perform most TC390 operations by issuing PPRC TSO (or ICKDSF PPRCOPY) commands from the
host system console to the XP1024/XP128/XP12000/XP10000. Using PPRC commands, you can
establish and delete remote copy communication paths; establish, suspend, resume, and delete TC390
Synchronous and TC390A pairs/groups; and view TC390 path and pair status. For more information on
using PPRC TSO and ICKDSF commands with the XP1024/XP128/XP12000/XP10000, see ”Using PPRC
Commands for TrueCopy” on page 153.
For operating systems that do not support PPRC, TC390 through Command View XP or XP Remote Web
Console is used to control and monitor TC390 operations. In this case, TC390 provides only
state-change-pending (SCP) notifications with service information messages (SIMs).
Restrictions. If you plan to use PPRC commands instead of the TC390 software to perform TC390
operations, the following restrictions apply:
• SVP mode 114 (see Table 4
on page 20) must be enabled to allow automatic port configuration in
response to PPRC commands. To fully support an automated environment, the
XP1024/XP128/XP12000/XP10000 is capable of automatically configuring a serial port as an RCP
or LCP, or a Fibre Channel port as an initiator or RCU target port if required in response to the TSO
CESTPATH and CDELPATH commands. However, even if you set ON for SVP mode 114, initiator ports
will not automatically change to RCU target ports, nor vice versa, when these ports are in
initiator/external mix mode. The XP1024/XP128/XP12000/XP10000 will verify that the specified
MCU port is offline to the host and will automatically configure it as an RCP or initiator port if required.
Similarly, the corresponding RCU port will also be configured as an LCP or RCU target port if required.
When the CDELPATH command is issued, the TC390 logical paths are removed, and if there are no
more TC390 or TC logical paths on the port, the port is automatically changed from RCP mode to LCP
mode, or from initiator port mode to RCU target port mode.
NOTE: For Fibre Channel interface, do not use the CESTPATH and CDELPATH commands at the
same time as the SCSI path definition function of LUN Management. The Fibre Channel interface
ports need to be configured as initiator ports or RCU target ports before the CESTPATH and
CDELPATH commands are issued.