Hitachi Universal Storage Platform V Reference Manual page 70

Mode Category
697 TrueCopy Async,
TrueCopy for z/OS
Async,
ShadowImage,
ShadowImage for
z/OS
701 Universal Volume
Manager
704 OPEN and
mainframe
3-26
Hitachi Universal Storage Platform V/VM User and Reference Guide
This option prevents the SI Split command execution when
the coordinated TCA pair status is Suspend, and its
Consistency state is not guaranteed.
Mode 697 = ON: SI Split is not executed when the
coordinated TCA pair status is Suspend, and its Consistency
state is not guaranteed.
Mode 697 = OFF: SI Split is executed regardless of the pair
status or Consistency state of the coordinated TCA.
Note: This option should be applied only to prevent SI Split
when the following conditions 1 and 2, or 1 and 3 are met.
1. TCA S-VOL and SI P-VOL coexist (for either mainframe or
open).
2. The TCA that is coordinated with SI has not been in
Suspend.
3. The TCA that is coordinated with SI is in Suspend, and its
Consistency is not in the latest state.
This option is used to issue the Read command at the LU
discovery operation using UVM.
Mode 701 = ON: The Read command is issued at the LU
discovery operation.
Mode 701 = OFF: The Read command is not issued at the LU
discovery operation.
Note:
When the Open LDEV Guard attribute (VMA) is defined on
an external device, set the system option to ON.
When this option is set to ON, it takes longer time to
complete the LU discovery. The amount of time depends on
external storages.
With this system option OFF, if searching for external
devices with VMA set, the VMA information cannot be read.
To reduce the chance of MIH, this option can reduce the
priority of SI, VM, CoW Shapshot, Flash Copy or Resync copy
internal IO requests so that host IO has a higher priority. This
mode creates new work queues where these jobs can be
assigned with a lower priority.
Mode 704 = ON: Copy processing requested is registered into
a newly created queue so that the processing is scheduled
with lower priority than host I/O.
Mode 704 = OFF: Copy processing requested is not registered
into a newly created queue. Only the existing queue is used.
Note: If the PDEV is highly loaded, the priority of Read/Write
processing made by SI, VM, CoW Shapshot, Flash Copy or
Resync may become lower. As a consequence the copy speed
may be slower.
Functional and Operational Characteristics
Function Default MCU/RCU
OFF MCU/RCU
OFF –
OFF –