Rob Zijlstra wrote:
> On Wed, 16 Nov 2005 06:55:09 -0800, DA Morgan <damorgan_at_psoug.org>
> wrote:
>
>
>>gazzag wrote:
>>
>>>>>Except that a sequence, as demonstrated, actually won't on a
>>>>>multi-user system.
>>>
>>>
>>>Yes it will. That sequence will give you numbers in ascending order
>>>which is what the OP asked for. Whether they're sequential or not is
>>>irrelevant.
>>
>>A common belief but not necessarily true.
>>
>>A sequence, by default, caches 20 numbers in memory. The order in
>>which those numbers are retrieved from memory is not guaranteed
>>to be in ascending order ... or any order.
>>
>>It is true that during testing on stand-alone single-user instances
>>they always are. But go to a multi-user system with high-activity
>>and your mileage may vary.
>
>
>
> Not necesary: ( Orcale 10G)
>
> NOCACHE Specify NOCACHE to indicate that values of the sequence are
> not preallocated. If you omit both CACHE and NOCACHE, the database
> caches 20 sequence numbers by default.
>
> Morgan, did you ever test (I did NOT)
>
>
> 0)
> CREATE SEQUENCE TEST.RRR
> START WITH 0
> INCREMENT BY 1
> MINVALUE 0
> NOCACHE
> NOCYCLE
> NOORDER
>
> 1) select TEST.RRR%Nextval into X from dual
>
> 2) use 1 value from this statement ( I then get X = 1)
>
> 3) Pull out the plug: Oracle dies at once ( no power)
>
> 4) Put power back on
>
> 5) Issue 'select XXX_seq%Nextval from dual'
>
> 6) What do I get?? ( if I use default settings) X = 2 or X = 22 ?
>
> Thank you
>
>
> Best Regards
>
> Rob Zijlstra
You will find a demo in Morgan's Library of this though I used
SHUTDOWN ABORT rather than pulling the plug.
--
Daniel A. Morgan
http://www.psoug.org
damorgan_at_x.washington.edu
(replace x with u to respond)
Received on Sat Nov 19 2005 - 16:35:22 CST
