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When you install or remove DIMMs, the server configuration information changes.
Therefore, you must change and save the new configuration information by using
the Configuration/Setup Utility program. When you restart the server, the system
displays a message indicating that the memory configuration has changed. Start
the Configuration/Setup Utility program and select Save Settings. If you need
instructions, see Chapter 2. Configuring your server in the User's Guide on the
IBM Documentation CD.
Active Memory:
Active Memory is an IBM feature that improves the reliability of
the DIMMs through Memory Mirroring, Memory Scrubbing and Memory ProteXion
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Memory Mirroring allows you to improve the memory reliability of your server by
creating a mirror of the data in memory port one and storing it in memory port two.
Note: For Memory Mirroring to work, you must have the same amount of memory
in both memory ports. For more information about the memory ports, refer
to the DIMM considerations 32.
Complete the following steps to enable Memory Mirroring.
1. Check your operating system documentation to be sure that it supports Mem-
ory Mirroring.
2. Install DIMMs of the same size and clock speed in the two memory ports.
3. Enable Memory Mirroring in the Configuration/Setup Utility:
a. Turn on the server and watch the monitor screen.
b. When the message Press F1 for Configuration/Setup appears, press
F1.
c. From the Configuration/Setup Utility main menu, select Advance Fea-
tures.
d. Select and enable Memory Mirroring.
e. Save and exit the Configuration/Setup Utility program.
How does Memory Mirroring work?
When Memory Mirroring is enabled, the data that is written to memory is stored in
two locations. One copy is kept in the memory port one DIMMs, while a second
copy is kept in the memory port two DIMMs. During the execution of the read com-
mand, the data is read from the DIMM with the least amount of reported memory
errors through Memory Scrubbing, which is enabled with Memory Mirroring.
If Memory Scrubbing determines the DIMM is damaged beyond use, read and
write operations are redirected to the remaining good DIMM. Memory Scrubbing
then reports the damaged DIMM and the Light Path Diagnostics display the error.
After the damaged DIMM is replaced, Memory Mirroring then copies the mirrored
data back into the new DIMM.
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Memory Scrubbing is an automatic daily test of all the system memory that
detects and reports memory errors that might be developing before they cause a
server outage.
Note: Memory Scrubbing and Memory ProteXion work in conjunction with each
other and do not require Memory Mirroring to be enabled to work properly.
How does Memory Scrubbing work?
When an error is detected, Memory Scrubbing determines if the error is recover-
able or not. If it is recoverable, Memory ProteXion is enabled and the data that
was stored in the damaged locations is rewritten to a new location. The error is
then reported so that preventative maintenance can be performed. As long as
Chapter 2. Installing options
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33
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