Inflow control of recordsets, Inflow control of, Recordsets – HP StorageWorks XP Remote Web Console Software User Manual
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Hitachi TrueCopy for z/OS user guide
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MCU power-off sequence is initiated, and also maintain sequence numbers in periods of low host
activities.
Figure 4
Selecting and settling TrueCopy Async recordsets at the RCU
Inflow control of recordsets
As described in the previous sections, both the MCU and RCU create sidefiles for storing TC390A
recordsets. Because the sidefiles occupy exclusive space in cache, both the MCU and RCU perform inflow
control to prevent an overload of the disk array’s cache resources. The XP12000/XP10000 uses the
following parameters (specified on the TC390 Async Option window, see ”
page 108) for TC390A cache inflow control:
•
Sidefile Threshold = maximum cache % available for use by TC390A sidefiles.
shows the TC390A sidefile threshold values and describes the actions that occur when each threshold is
reached.
• 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 system option
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 ”
• 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.