HP StorageWorks XP Remote Web Console Software - Manual (Page 32)

32 TrueCopy for the XP128/XP1024/XP10000/XP12000
• The “high-water mark” (HWM), which is the sidefile threshold minus 20%, indicates when
graduated delay begins for TC390A volume pairs (see the following section). If SVP mode 118 is
ON, a warning SIM is also generated.
• The puncture threshold, which is the sidefile threshold plus 10%, indicates when the TC390A pairs
will be suspended due to sidefile overflow (see ” CESTPATH ” on page 150).
• Inflow control by MCU: When the amount of MCU sidefile cache reaches the HWM, the MCU
responds to update I/Os from the host with state-change-pending (SCP) or channel-command-retry
requests and begins graduated delay.
• Inflow control by RCU: When the amount of RCU sidefile cache reaches the HWM, the RCU
responds with channel-command-retry requests to the RIO commands, which transfer the recordsets
from the MCU. The only recordset accepted by the RCU is the recordset with the sequence number
required to continue settling pending recordsets.
• Offloading Timer = maximum time between TC390A recordset transfers.
• Inflow control by MCU: If the MCU is not able to send a recordset to the RCU within the
user-specified offloading timer value, the MCU suspends all TC390A pairs and resets the SCP
condition to avoid hanging up the system.
• Inflow control by RCU: If the RCU is not able to settle a recordset within the user-specified offloading
timer value, the RCU suspends all TC390A volume pairs and resets the channel-command-retry
condition to avoid hanging up the MCU.
HXRC. HXRC operations use a different cache sidefile than TC390A. Table 7 on page 33 also shows the
sidefile threshold values for HXRC operations and describes the actions that occur when each threshold is
reached. Disk arrays performing TC390A in combination with HXRC must have sufficient cache installed to
handle the increased sidefile activity. If a “sidefile puncture” condition occurs (HXRC sidefiles reach 10%
over threshold), the XRC session having the highest sidefile usage is terminated.
SIM reporting for sidefile conditions is disabled when mode 118 is OFF (
Table 3 on page 20).
NOTE: Cache LUN XP operations may decrease the total amount of cache available for TC390A and
HXRC operations, but do not directly affect sidefile cache usage. Available cache is defined as the amount
of physical cache memory installed on the disk array minus any cache reserved for the Cache LUN XP
feature.
Table 7 Sidefile thresholds
Operation Threshold(s) Action(s)
TC390A High-water mark (HWM) = sidefile threshold –
20%
MCU (RCU) reaches HWM: command
retry to host (MCU), begin graduated
delay. Delay times can be adjusted using
mode 93 (see Table 3 on page 20).
Sidefile threshold = 30-70% of cache, default =
50%.
TC390A threshold can be adjusted from 30-70%
(in 10% increments) using TC390 through
Command View XP or XP Remote Web Console.
MCU (RCU) reaches threshold: command
retry to host (MCU), max delay time (500
or 100 ms). Delay time can be adjusted
using mode 93 (see Table 3 on page 20).
Puncture threshold = sidefile threshold + 10% MCU (RCU) reaches puncture: suspend
affected TC390A pairs due to sidefile
overflow condition.
HXRC 1 [XRC sidefile] / [avail cache] = 40%, 50%, 60%
XRC thresholds can be adjusted by using modes 85
and 86 (see Table 3 on page 20).
Threshold 1/2/3 = 30/40/50%, 40/50/60%, or
60/70/80%
Threshold 1 = command retry.
Threshold 2 = SCP message.
Threshold 3 = puncture condition.
Write Pending [write pending] / [avail cache - sidefile] = 70% Command retry.