Question & Answer
Question
After updating to 10.5FP7 from an older fixpack level, I noticed that AUTOMATIC value for NUM_IOSERVERS is changed even though any settings are not changed. Is it expected bahavior?
Answer
Yes, it is expected. Due to IT09990, we changed the fomula for calculating the number of prefetchers to start at database activation time.
Until 10.5FP6, we use following fomula:
number of prefetchers =
max( max( max over all table spaces( parallelism setting ),
number of cores * number of SMT threads ), 16 )
Starting from 10.5FP7, we use following fomula:
number of prefetchers =
max( max( max over all table spaces( parallelism setting ),
number of cores * number of SMT threads ), 12 )
So you can see the following output in 10.5FP6 and FP7:
FP6:
$ db2 get db cfg | grep NUM_IOSERVERS
Number of I/O servers (NUM_IOSERVERS) = AUTOMATIC(16)
FP7
$ db2 get db cfg | grep NUM_IOSERVERS
Number of I/O servers (NUM_IOSERVERS) = AUTOMATIC(12)
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Modified date:
16 June 2018
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