Fetching records in a block(db) for mass processing

Question

My user interface inputs commit frequency for intermittent commits. We reference this to # of records processed & then issue commit. [whilst processing against millions of records]
Now, we want to process all records belonging to set of data blocks to avoid contention issues (gc/ other locking issues) & then issue commit.
So the question is, how do I query records belonging to a particular block OR identify those blocks that hold my data.
Any pointer is greatly appreciated.
thanks
Kiran.

Answer 1

kkulkarn wrote:
This is needed for a DW instance wherein we select recordset from a OLTP instance running 4 node RAC. The user then inputs a condition based on which the records are selected.
We are commiting based on parameters defined by DBA's - the commit frequency. This increases contention especially if the records are stored in contiguous location. Add to this the RAC, the GC traffic is huge.
So what we want to do is to grab all the records in a particular block & read the whole block & then process to DW. I was looking at a query that can get me the block# involved in this process.
Could you clarify:
Is it the OLTP that is on RAC, or the DW, or both ?
Which type of contention - can you show us the critical wait information - and is this on the OLTP or RAC system, and is it the OLTP or RAC system where the GC traffic is huge ?
You seem to be asking how you can specify a query in an OLTP system that is going to visit many table blocks - but "pre-sort" the data in some way so that it visits each table block only once, and visits the table blocks in order so that you don't revisit the same table block and run the risk of extra interconnect traffic on the OLTP system. Is this a correct interpretation of your requirement ?
Does your transfer process do something like:
counter := 0;
for r in (select from OLTP system) loop
    insert into DW system values (r.thing....);
    counter := counter + 1;
    if counter = {limit} then
        commit;
        counter := 0;
    end if;
end loop;
commit;Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk
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