Help calculating load values

I need some help calculating how much activity a query causes.

If I have a table defined as:
create table test_a (
col1 integer,
col2 char(1),
col3 varchar(35),
primary key (col1,col2)
) with oids;

When I do an "insert into test_a values (1,'a','test data');", does this
generate 3 writes (1 to table, 1 to index, and one to oid counter) and one
read (get oid from oid counter)?

What about when I do an "update test_a set col3='changed data' where col1 =
1 and col2 = 'a';"? I am thinking 5 writes (1 to old table tuple, 1 to old
index tuple, 1 to oid counter, 1 to new table tuple, one to new index tuple)
with 1 read (get oid from oid counter)?

Finally, what about the delete "delete from test_a where col1=1 and
col2='a';"? 2 writes (1 to table tuple, and 1 to index tuple)?

I am just trying to get a grasp on how much traffic I am creating for each
major dml statement we issue so that I can work with my sysadmin on some i/o
issues.

Thanks,

Chris

PG 8.1
RH 4

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