Re: Online create index or reindexing?
Thanks a lot. One more thing. Will create index still scan the table even though some other index has all the columns needed for my index. E.g. I want to create index on col1 and another index has the...
View ArticleCache Turnover
I'd like to come up with some kind of metric, using the MDA tables, which would show cache turnover. Maybe a number, maybe a percent? I'm not sure. I just want to gauge the magnitude of memory...
View ArticleUpdate index statistics causes number of histograms to reduce
I guess there is issue with update index statistics. Create index on any table and check the optdiag output for the leading column and number the histograms. Now just update the statistics using...
View ArticleRe: Update index statistics causes number of histograms to reduce
Hi, You need to qualify those findings with some evidence, it shouldn't be a generic issue effecting all tables/indices/row counts/data distributions. Do you have before and after optdiag outputs?...
View ArticleRe: Update index statistics causes number of histograms to reduce
I cant put table definitions from my system. I have observed it almost on all of the table where column has say more than 1000 distinct values and overall row count is more than 500K. Below is what you...
View ArticleRe: Update index statistics causes number of histograms to reduce
Based on this statement in the documentation: update index statistics uses the current number of steps in the existing histogram when it creates a new histogram. The number of histogram steps...
View ArticleRe: Update index statistics causes number of histograms to reduce
Yes that is what documents says. Also, it should not reduce the number of steps unless you are reducing it using a different step values. If it is doing quite frequently then I guess it must be causing...
View ArticleRe: Update index statistics causes number of histograms to reduce
Hi, It seems likely that this is a nuance of the ever increasing distribution of each col2 value. What is does kind of show is that when you build an index it doesn't build an index and then run update...
View ArticleRe: Update index statistics causes number of histograms to reduce
I have seen this in other tables as well. Anyway, I guess it could be an issue with the sybase on how it handles the histogram. I will talk to sybase support team. Thanks
View ArticleRe: Update index statistics causes number of histograms to reduce
what is the locking scheme for these tables?
View ArticleRe: Update index statistics causes number of histograms to reduce
Some are all pages and other are data rows.
View ArticleRe: Update index statistics causes number of histograms to reduce
have a look at http://search.sybase.com/kbx/solvedcases?id_number=11663936 From solved cases this might be related to CR664877. For what it's worth, I can't reproduce your problem on 15.7 SP101, but I...
View ArticleRe: Update index statistics causes number of histograms to reduce
For CR 664877, a key feature is that the table has a number of partitions (the test case was a table that had 9 roundrobin partitions). CREATE INDEX generates statistics on each partition and then...
View ArticleRe: Update index statistics causes number of histograms to reduce
FYI, I ran Darshan's repro on a 15.7 SP103ish bin_iso_1 2KB server using apl locking and server level histogram steps=50/tuning factor 20. Ended up with 500 after index creation and 175 steps after...
View ArticleRe: Update index statistics causes number of histograms to reduce
This is not only issue but there are other issues and some of them which i consider very bad are below. 1. dpaecrcnt, ipagecrcnt,drowcrcnt are not correct when you create index and that is due to...
View ArticleRe: Update index statistics causes number of histograms to reduce
Hi, Without going into the details, what your major concern should be is do these estimate differences give you plan flips? If you have a a situation where (on latest version) drop index a (a single...
View ArticleRe: Update index statistics causes number of histograms to reduce
Yes, I had the issue with all of these..But I fixed them by changing my update stats by using more steps, After that I never had any issues. ThanksDarshan
View Article