Sequence generation issue

Question

Hi , I am working in Healthcare industry . we have a claim and payment matching process . Every day 1.5 million payments get matched with 70 million claims and the matched payments are stores in some output table . After matching, an oracle seqence number is generated for each matched record and that is the primary key for the output table.
Match query will be like this,.
Select seqeunce1.nextval,a.column1,a.column2,b.coulmn1,b.column2 from claim_table a, payment_table b
where a.column3=b.column3
We are facing some seqence problem here. some sequence are missed during the first day and the missed sequnces are getting generated in the second day.
Sequence Query:
CREATE SEQUENCE ERA_CLAIM_MATCH_S
START WITH 1
MAXVALUE 999999999999999999999999999
MINVALUE 1
NOCYCLE
CACHE 500
NOORDER;
Example to demonstrated the problem:
Day 1(15th July) : sequence generated from 1 to 1000000 (some sequence are missed in between)
Day2 (16th July) : sequence generated from 2500 to 2000000 (some missed sequence in day 1 are generated here)
Our database in in RAC system.

Answer 1

Hemant K Chitale wrote:
I think that the question is : If the highest value generated on Day 1 was 1000000,  how could a value of 2500 be generated on Day 2 ?
Shouldn't happen if the Sequence is a NOCYCLE.Hemant, but that is possible if Day 1's processing used the sequence on RAC instance 1 - whereas on Day 2, RAC instance 2 (with unused cached sequences from yesterday) is used.
E.g.
// on node 1
SQL> create sequence testseq start with 1 increment by 1 nomaxvalue nocycle;
Sequence created.
SQL> select testseq.nextval, sys_context( 'user', 'instance_name' ) as instance from dual;
   NEXTVAL INSTANCE
         1 dev_1
// on node 4
SQL> select testseq.nextval, sys_context( 'user', 'instance_name' ) as instance from dual;
   NEXTVAL INSTANCE
        21 dev_4
// on node 1, use the sequence a couple of times
SQL> declare i integer; begin loop i := testseq.nextval(); exit when i > 100000; end loop; end;
  2  /
PL/SQL procedure successfully completed.
SQL> select testseq.nextval, sys_context( 'user', 'instance_name' ) as instance from dual;
   NEXTVAL INSTANCE
    100002 dev_1
SQL>
// on node 4, check the sequence
SQL> select testseq.nextval, sys_context( 'user', 'instance_name' ) as instance from dual;
   NEXTVAL INSTANCE
        22 dev_4