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Model PDP Series 200 maxDPU4E Hardware Guide

Using the Takeover Button

Pressing the Takeover button can force a previously inactive DPU to go

active. This should not be done casually as a manually forced takeover

occurs regardless of the inactive DPU’s ability to control. This can have

severe consequences to your process.

If the Takeover button is pressed on an inactive standalone DPU (i.e., backup

is not enabled), the inactive DPU will go active regardless of its health,

database, or key switch position.

If the Takeover button is pressed on the inactive DPU of a DPU pair (backup

enabled), the inactive DPU will go active regardless of its health or key

switch position as long as it is hot. A “hot” DPU is one that has a database

that matches that of the other member of its pair (including the case where

neither DPU has a database).

Once takeover occurs, the now inactive DPU will “warm” (synchronize) its

database from the now active DPU. This will force the inactive DPU’s

database to match that of the active DPU. When the inactive DPU becomes

“hot”, it will automatically go active and take back control as long as it

determines that its health is better than that of the active DPU. This will force

the suddenly inactive DPU to declare a fatal error and halt. Only a reset will

clear the fatal error condition and take it out of this mode. This behavior is

necessary to prevent the DPU pair from oscillating back and forth forever as

they alternately take control away from each other.

If you wish to guarantee that an inactive DPU goes active and stays active,

you must “kill” the currently active DPU. This can be done by either

unplugging the DPU from its chassis or by writing to the “ForceFatal”

attribute of the active DPU.

Pressing the Takeover button on an active DPU has no effect.

Metso Automation MAX Controls Inc. • 278590 •

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Adaptec 1542B - AHA Storage Controller Fast SCSI 10 MBps Spezifikationen Seite 20