Wassim,
Here is a list of possible reasons why values of sequence numbers may
be lost.
- Individual sequence numbers can be skipped if they were generated and
used
in a transaction that was ultimately rolled back. The sequence is
incremented independent of the transaction committing or rolling back.
This will occur regardless of the sequence being cached.
- The same sequence can be used for one or multiple tables. It is
possible that individual sequence values may appear to be skipped
because
it is being used for multiple tables.
- If a sequence is cached, the unused cached sequence values may be lost
if
there is a system failure (shutdown abort or system crash).
- If the value of "SEQUENCE_CACHE_ENTRIES" "init.ora" parameter is too
low,
it is possible to skip sequence values. If the number of cached
sequences
is greater than "SEQUENCE_CACHE_ENTRIES", then a sequence cache may be
aged out of the SGA. If a request is made for a sequence that is not in the
cache and there are no free entries, the oldest on the LRU list is deleted
and replaced with the newly requested one. All of the remaining values
in
the displaced sequence are lost.
- In 7.3 the functionality of the caching of sequences was changed. Prior
to 7.3, the sequence cache was kept in the row cache. In 7.3+ the
sequence cache was moved to the library cache. Oracle Bug 432251
identified the cached sequence was being aged out of the library cache too
rapidly. This
bug is fixed in 7.3.4.
I hope this helps.
Wassim <net2000_at_francemel.com> wrote in message
news:7l5kd2$qi9$1_at_nnrp1.deja.com...
> Hi,
> I'm using Sequences (as many of you told me to do, for generating a
> primary keys in some tables) Strange phenomenen i've noticed is that in
> some cases counter jumps from 21 to 40 or 11 to 34 ? this is source of
> my sequences :
>
> create sequence mvt_seq
> start with 0
> increment by 1
> nomaxvalue
> minvalue 0
> nocycle
> order (cos order is important for me!)
>
> Is there any problem with this?
> Thanks for help!
>
> Wassim.
> e-mail: net2000_at_francemel.com
>
>
> Sent via Deja.com http://www.deja.com/
> Share what you know. Learn what you don't.
Received on Mon Jun 28 1999 - 06:00:34 CDT
