Hello Jinwoo,
Thanks for your interest and replay.
To check statistics governor is woring I check update_time in SYSCOLSTAT by query
select SYS.SYSTABLE.table_name,SYSCOLSTAT.*
from SYSCOLSTAT
join SYS.SYSTABLE on SYS.SYSTABLE.table_id = SYSCOLSTAT.table_id
where SYS.SYSTABLE.table_name = 'some tables...'
and in some columns update_time is acutal I think it is from last checkpoint, but there is also some columns which update_time is old 3 - 5 days. I don't know is this old updata_time of statistics are ok ?
On copy of production database I make test by using query which is run by my ERP (very slow) and total runtime from execute query in PlanViewer is 20s, After test I make CREATE STATISTICS on all tables from this query and runtime is aprox 1 - 2 s. That is big difference.
Another question is if I make CREATE STATISTICS on all tables in database this not delete any data or links or other information from my production database ?
On SyBooks Online I found that information
"Old statistics are not loaded when a database is rebuilt When you rebuild a version 11 or earlier database, the LOAD STATISTICS statement silently skips loading old string statistics into the new database, but upgrades the version of the string statistics. See LOAD STATISTICS statement."
Should I make some specific thing with statistics after rebuild from 11 to 12 ?
Regards,
Marek