>mohitanchlia@gmail.com
>Version: IDS 10
>I am trying to determine the optimal value for DS_POOLSIZE and
>DS_HASHSIZE. I looked at the onstat -gdsc. I have following question:
>
>1. How do I determine the correct size of DS_POOLSIZE. Should I look
>at our update stats and see number of unique columns that we run
>update statistics on and that would become the value of DS_POOLSIZE.
>2. How do I determine correct value of number ofHash Buckets ? How
>many entries per bucket is good to have ?
>3. WhenI look at onstat -g dsc I see number of distribution entries,
>should this be always lower than DS_POOLSIZE
Hi,

1. Use the following processto get DS_POOLSIZE and DS_HASHSIZE

-Identify the number
of columnsthat have distributions set for the existing Instance of IDS.
-Take thisvalue and multiply it by 1.1 to account for any additional overhead, plus to give a little buffer to reduce overflow possibilities.
-Divide this number by the depth you want each bucket to be, typically between 4 and 10.
-Find the closest prime number to this generated value that is greater than the generated value. This prime number is what should be set as the DS_HASHSIZE value.
-Multiply your new DS_HASHSIZE by the same value you originally divided by in order to obtain your DS_POOLSIZE.
-Additional tuningmay be required

2. Generally 4 is enough for the dept of the buckets.Think of DS_HASHSIZE as an array, but think of the depth of the buckets asa linked list.

3. Yes. If is it around or > than 75%, you are going to start cleaning the cache, if you are at 100% you not only are tuned too low, but you also are adding entries to the
cache faster than you can clean the cache.