Note: The following article was published in the IBM Journal of Research and Development  (Volume:56 ,  Issue: 1.2 ).  

The IBM zEnterprise system introduced a new and innovative redundant array of independent memory (RAIM) subsystem design as a standard feature on all zEnterprise servers. It protects the server from single-channel errors such as sudden control, bus, buffer,
and massive dynamic RAM (DRAM) failures, thus achieving the highest System z memory availability. This system also introduced
innovations such as DRAM and channel marking, as well as a novel dynamic cyclic redundancy code channel marking. This paper
describes this RAIM subsystem and other reliability, availability, and serviceability features, including automatic channel error recovery; data and clock interface lane calibration, recovery, and repair; intermittent lane sparing; and specialty engines for maintenance, periodic calibration, power, and power-on controls.

The full text of the article is available at the below link:

IBM zEnterprise RAIM.pdf