cache buffer lru chain latch

   

we have a table with following stats

select sum(bytes)/1024/1024 from user_segments --> 2.8 GB

count(*) --> 3,547,629

select sum(blocks) from user_extents --> blocks 716,800

block_size=4K

SGA_TARGET=5600M
db_recycle_cache_size=1G
db_keep_cache_size=608M

As part of our application enhancements, we need to add 10 columns to this table

alter table shipment_header_aux_bak add(trailer_plate_no char(20 byte) default ' ' not null);

Above alter table statement took about 17 minutes that means that in order to add 10 columns,
it would take 170 minutes. We need to speed up the process for this statement so we ran 10046 session trace