At 01:16 PM 3/31/2002 +0000, csswa wrote:

>It's also strange that a backup on this db takes about two minutes
>(ditto for restore) since a sweep is also part of that process.

Actually, a sweep is not part of a backup. Because backup reads
every record it does remove unnecessary record versions and rolled
back records up to the oldest active transaction. However, you
can disable garbage collection on backup and speed up the process
a lot. That makes sense if you plan to restore the backup immediately -
why bother to clean up something you're going to delete?

Sweep does the same clean-up then reads the transaction inventory
pages, changing the state of rolled back transactions to committed
once their updates have been eliminated.

It seems unlikely that the transaction fixup took 14 minutes. Did
you disable garbage collection in your backup. One reason for long
backups with garbage collection enabled is an index with a large
number of duplicate values. The number depends on the page size
and the page buffer count, but oddly not on the key size. If you
have such an index, you might consider adding a more selective
value (e.g. the primary key) to the index to reduce garbage collection
time.

Regards,

Ann
www.ibphoenix.com
We have answers.


Question for anglophones. When I was growing up, the three words "trash",
"garbage", and "rubbish" had different meanings. Now, they are generally
(except by me) used interchangeably, except in a metaphorical sense.
"Trash talk", "garbage mouth", and "utter rubbish" convey quite different
meanings, but trash, garbage, and rubbish are interchangeable.

To me, trash is paper and other dry combustible home detritus. Garbage
is food waste, collected by the pig man, if he got there before the
skunks. Rubbish is non-combustible. Consider a can of tomatoes that's
past its expiry date. The tomatoes are garbage, the can is rubbish,
and the label is trash. These days, I guess, the metaphorical distinctions
are more significant than the real ones and the whole thing is rubbish
to be chucked in the garbage can and collected by the trash man.

Here endth the lecture.