IBM eServer xSeries 445 Type 8870 Option Installation Manual page 53

Figure 40. DIMM installation
Active Memory
Active Memory is an IBM technology that improves the reliability of the DIMMs
through the memory mirroring, memory scrubbing, and Memory ProteXion
features.
The following notes describe the Active Memory features:
v Memory mirroring: This feature enables you to improve the reliability of the
memory in your server by creating a mirror of the data in memory port 1 and
storing it in memory port 2. (See "Enabling or disabling memory mirroring" on
page 42 for instructions.)
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 1 DIMMs, while a second
copy is kept in the memory port 2 DIMMs. During the execution of the read
command, the data is read from the DIMM with the least number of reported
memory errors through memory scrubbing, which is enabled with memory
mirroring.
If memory scrubbing determines that a DIMM is damaged beyond use, read and
write operations are redirected to the remaining good DIMMs. Memory scrubbing
then reports the damaged DIMM and the light path diagnostics feature displays
the error. After the damaged DIMM is replaced, memory mirroring then copies the
mirrored data back into the new DIMM.
v Memory scrubbing: This is an automatic daily test of all the system memory
that detects and reports potential memory errors before they cause a server
outage.
Note: Memory scrubbing and Memory ProteXion technology work with each
other and do not require memory mirroring to be enabled to work.
When an error is detected, memory scrubbing determines whether the error is
recoverable. If it is recoverable, Memory ProteXion is enabled and the data that
DIMM
Chapter 2. Installing options
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