Oracle MOSC Note: 223117.1 has some great advice for tuning-down
“db file scattered read” waits by detecting fragmented indexes:
If indexes are fragmented, again we have to visit more blocks
because there is less index data per block. In this case, rebuilding
the index will compact its contents into fewer blocks.
This note also show that the use of multiple blocksizes helps to
reduce buffer stress:
As blocks read using Full Table and Fast Full Index scans are
placed on the least recently used end of the Buffer Cache
replacement lists, sometimes it may help to use Multiple Buffer
Pools and place such segments in the KEEP pool. For more
information please refer to [NOTE:76374.1] Multiple Buffer Pools
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