Updating large volume of records

Question

I have a table having more than 10 mil records and I have to update multiple columns of this table from the data which I get from few other tables which again have large number of records. All the tables are indexed

I tried doing it in batches and updating in concurrent sessions but it it taking very long time. Is there any alternative approach for this problem?

Answer 1

Solution is to build a brand new table(with nologging) and to parallelize.

1) First create your dummy hold table (with no rows):

create table xyz_HOLD as select * from xyz where rownum<1

Avoid logging all these operations*...

Alter table xyz_HOLD nologging

*With nologging, if the system aborts, you simply re-run the 'update' again, as you have the original data in the main table

2)

    insert /*+ append parallel (xyzhold,12) */ 
      into xyz_hold xyzhold (field1, field2, field3) 
    select /*+ parallel (x,12) */ xyz.field1, my_new_value_for_field2, xyz.field3 
      from xyz x 
     where blah blah blah 

3) when done, either rename the table, or swap the partition if your original table is partitioned, and you only updated one partition as we do.

+) Obviously you also need to rebuild indecies, etc as required afterwards.