Graduated delay sidefile management, Dummy pair mode, 5 graduated delay process for sidefile management – HP StorageWorks XP Remote Web Console Software User Manual
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Graduated Delay Sidefile Management
The following figure shows the graduated delay process for TC390A sidefile management. When the
TC390A sidefile value reaches the high-water mark (threshold minus 20%), the
XP128/XP1024/XP10000/XP12000 begins command retry delay for host updates to TC390A M-VOLs
and reports a warning SIM to the host. As the amount of sidefile increases, the delay increases
incrementally as shown in the following figure. Use Mode 93 on the XP128/XP1024/XP10000/XP12000
on page 20) to select the delay type (long or short). This graduated delay
methodology minimizes the potential for sidefile overcommitment, while at the same time providing another
level of automation control.
SIM reporting for TC390A sidefile conditions is enabled only when SVP mode 118 or 464 is ON (see
on page 20). The reported SIMs when SVP mode 118 or 464 is ON, however, do not support a
CLPR. When this SIM is reported to the host, the SIM reference code is indicated as 490x-yy (“x” is CU
number, and “yy” is LDEV number). For more information about the SIM reference code, call your
HP Account Support Representative.
You can disable the command retry delay for a limited number of critical volumes using the special “No
delay” parameter for the CESTPAIR TSO command (see ”
” on page 152). When this parameter
is set, the XP128/XP1024/XP10000/XP12000 will not delay host write I/Os to the M-VOL until the
TC390A sidefile amount reaches the puncture threshold (threshold + 10%). This prevents performance
degradation for critical volumes and should be used only for a small number of volumes.
Figure 5
Graduated delay process for sidefile management
Dummy Pair Mode
TC390A performance can be limited due to RIO response through CNT/ATM. This is because only one
RIO at a time can transfer updates to remote side. RIO is issued with the device address of secondary
volume. ESCON protocol allows only one I/O at a time to the same device address. Dummy pair mode
addresses this limitation by providing additional device addresses for specific high-usage volumes.
1. For more information on sidefile thresholds for HXRC operations, refer to ”