Determining the block or CI size

There are several factors for determining the block size or the CI size.

  • A recommended general rule of thumb is a 4 KB block or CI size. However, if the average database record length reported in the Distribution of Database Record Sizes report is larger than 800 bytes, then a larger block or CI size could be tried.
  • If the average database record length is in the range of 800-1600 bytes, an 8 KB block or CI size is often a better bet.
  • If the average database record length is in the range of 1600-2400 bytes, a 12 KB block or CI size should be investigated.
  • For average database record lengths substantially longer than 2400 bytes, the first-guess method described in this topic often does not apply.

    Block or CI sizes larger than 12 KB should be an exception.

    Block or CI sizes smaller than 4 KB are seldom reasonable.