Re: alter table tabname drop column colname checkpoint #;

I had to read my book to find the answer to this one ;)

If you specify (at least under 8.1.5):

    alter table tabX drop column colX;
then there is no checkpoint and you generate the worst volume of rollback.

If you specify:

    alter table tabX drop column colX checkpoint NNN; then you checkpoint every NNN rows.

If you specify:

    alter table tabX drop column colX checkpoint; without a rowcount, then you checkpoint every 512 rows.

You post doesn't include the checkpoint keyword, so I guess you hit the top option.

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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Author of:
Practical Oracle 8i: Building Efficient Databases

-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 26 March 2002 04:08

|OK, I asked this on Friday when people were thinking about going home
and I
|didn't get any answers... any takers?
|
|-----Original Message-----
|Sent: Friday, March 22, 2002 1:01 PM
|To: Multiple recipients of list ORACLE-L
|
|
|I've got a "process" which is consuming RBS to the point of failure
(running
|out of tablespace). I have very little control of the code so using
set
|transaction is not a possibility.
|
|The SQL that is failing is "alter table tabname drop column colname"
with no
|checkpoint being specified. According to the documentation, when no
|checkpoint integer is specified then it defaults to committing every
512
|rows but I suspect this is not happening hence the rollback problem.
Does
|anyone have experience with dropping columns on large amounts of data
and
|specifying the checkpoint integer? If you don't specify the
checkpoint does
|it really default to 512 like the documentation says? How would I
test the
|checkpoint default? (We're running Oracle 8172 on Linux.)
|
|As an alternative I'm thinking about doing an "alter table tabname
set
|unused column colname" then manually doing an "alter table tabname
drop
|unused columns" later with a set transaction.
|
|Any ideas?
|
|Steve Orr
|Bozeman, MT

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Author: Jonathan Lewis
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