Sorry, I left off the subject line on the original!

-----Original Message-----
Sent: Thursday, June 16, 2005 10:10
To: firebird-support@yahoogroups.com
Subject: [firebird-support]

I'm pretty new to this list. I should have signed up ages ago. There is
a wealth of information here.

Thanks to some of the recent posts about CPU usage and index selectivity
and database sweeping, I'm SLOWLY starting to understand the meaning of
gstat info that I never understood before. Perhaps someone who already
understands all of it could help me along.

1) In a gstat -h, what is the difference between "Oldest Active" and
"Oldest snapshot"? For instance, why might I see the following?
Oldest transaction 2896976
Oldest active 2896977
Oldest snapshot 2853644
Next transaction 2897181

2) Oldest transaction means "oldest interesting transaction" and is used
for auto-sweeping, right?
a) I don't need to be concerned if the Oldest Transaction is very
old, do I? Like the following?
Oldest transaction 38879
Oldest active 293593
Oldest snapshot 293585
Next transaction 293606

3) In a gstat -r -a, what is the difference between "total versions" and
"max versions"?
a) Does the average version length tell me anything useful?
b) I was under the impression that having an old "Oldest Snapshot"
would mean I would also have a high max versions, but the database cited
in (1) doesn't seem to. Here's the only interesting lines from that
database:
TABLE_Q
Average version length: 14.99, total versions: 4327, max
versions: 51
TABLE_X
Average version length: 42.16, total versions: 650, max versions:
1

4) What is the difference between total dup, and max dup for indexes? I
had a high max dup on the tables cited in (3b), so I did a compound
index with the primary key. But I still have a high "total dup"?
INDEX_Q
Average data length: 0.00, total dup: 2379, max dup: 28
INDEX_X
Average data length: 0.00, total dup: 29593, max dup: 32

Thanks!
Kevin



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