Skip Nexval of Sequence

Question

I have 3 sequence in one user
some time sequence next value skip some numbers
like if last sequence no was 10 it generate next value 21
some time only one no skip ...like last no 21 ... next value 23
all 3 sequence are getting some problem.
I created sequence
Sequence 1 :-
create sequence SJV
minvalue 1
maxvalue 9999999
start with 1
increment by 1
Order;
Sequence 2 :-
create sequence JV
minvalue 1
maxvalue 9999999
start with 1
increment by 1
Order;
Sequence 3 :-
create sequence voucherno
minvalue 1
maxvalue 9999999
start with 1
increment by 1
Order;

Answer 1

Kame wrote:
I am generating the sequence with the following method
No. 1
select fwqgl.voucherno.nextval GlVNo,t.* from
          select r_no,to_char(r_date,'YYYY') VYear, to_char(r_date,'MM') VPeriod,'SRV' Vtype,
          r_date Vdate,narration
          from fwqrecview
          where chk='Y'
No. 2
select fwqgl.SJV.nextval GlVNo,t.* from
                  select inv_no,to_char(inv_date,'YYYY') VYear, to_char(inv_date,'MM') VPeriod,'SJV' Vtype,
     inv_date Vdate, status, ('To record Invoice No.'|| inv_no ||' to '||Sh_name||' against '||v_name||' BL QTY '||bl_qty||'@'||Exc_rate||' x ' ||USd) Narration
     from fwqInvView
          where chk='Y'
No. 3
select JVno.nextval into :vouchermaster.vm_no from dual;I noticed that sequence no skip every day at morning (first entry) when user enter data in form.
after that all the day sequence give next val in serial accordingly.That would indicate that the sequence is cached then. Rather than it read a single value each time you ask for a sequence, the database reads the next X values (let's say 10 values for sake of argument), so that it can help with performance (albeit very very slightly). So the first request gets a sequence number and caches another 9, the next request can read the next value from that cache rather than having to do the additional processing of getting it from the sequence in detail. Now, while there are values cached in the databases memory, if the database is shut down and restarted (like probably happens overnight for you when backups are done I'm guessing etc.), the database loses that cache of numbers and has to start from the next one from the sequence again. This is the most likely cause of you seeing gaps first thing in the morning.
I also checked that when I change the system date and close all the forms and re-open and run .
it skip the next val.Yes, with Forms a similar caching can happen, so you can lose values in the same way.
This is not an issue, because this is how sequences work. There is no such thing as a gapless sequence and you shouldn't expect to ever get one.
The closest you can get is to create your sequence with the NOCACHE option, which will prevent the caching, but won't rollback the sequence if someone has fetched the nextval but rolled back their transaction.