I just migrated a database from 7.3.4 to 8.1.7.1 on Sun Solaris 2.6.
I do not believe that there were any statistics on this database before
it was migrated.
During the process of the migration, I followed the instruction and
switched optimizer_mode from rule to choose.
After it was upgraded, there were some pockets of extremely poor
performance. On a hunch, I looked at the last_analyzed date of
all my non-system tables. I was surprised to see that about a
third of the tables seemed to have "junk" statistics in existence
with a last_analyzed date of 00-000-00.
What might have caused these statistics to be out there? I doubt
that we had pre-existing statistics because I've had them prior
to upgrades and afterwards they've continued to have the same
valid dates on them as they had before the upgrade.
Anybody seen these "junk" statistics before? I got rid of them
and everything was fine but I'd like to prevent them from being
created the next time that we do a 7.3.4 to 8.1.7.1 upgrade.
Any light anyone can shed is appreciated.
Thanks,
Cherie
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