An insert NEVER locks a table to other DML. Other sessions can't see the records until the session doing the insert has committed.
Run sql_trace on your transaction or examine the SQL statements to check for:
* Update (and delete - although that's not likely to be in your transaction is it?)
* select ... FOR UPDATE; (FOR UPDATE locks the rows returned by the query until you commit/rollback).
You say there are 10 child tables. If these child tables are using referential integrity constraints (which they should) -- then Make extra sure that your foreign keys are indexed! If you don't, then locking a single record in the parent table will lock the entire child table -- not just the corresponding child records. This makes sense as the only way Oracle would be able to determine what the child rows are - is to scan the entire table for them. On a large table this would slow the app to a crawl - so it locks the entire table.
On your parent table, try this:
select * from dept where deptno=10 for update;
Then, from a different session - try to lock a different row on the child table:
select * from emp where deptno=20 for update nowait;
If you can't get the lock - try commit/or rollback from the first session and then try again.
Remember that you need to consider all child tables - not just the first level.
Run this query to find unindexed FK's:
select decode( b.table_name, NULL, '****', 'ok' ) Status,
a.table_name, a.columns, b.columns
from
( select substr(a.table_name,1,30) table_name,
substr(a.constraint_name,1,30) constraint_name,
max(decode(position, 1, substr(column_name,1,30),NULL)) ||
max(decode(position, 2,', '||substr(column_name,1,30),NULL)) ||
max(decode(position, 3,', '||substr(column_name,1,30),NULL)) ||
max(decode(position, 4,', '||substr(column_name,1,30),NULL)) ||
max(decode(position, 5,', '||substr(column_name,1,30),NULL)) ||
max(decode(position, 6,', '||substr(column_name,1,30),NULL)) ||
max(decode(position, 7,', '||substr(column_name,1,30),NULL)) ||
max(decode(position, 8,', '||substr(column_name,1,30),NULL)) ||
max(decode(position, 9,', '||substr(column_name,1,30),NULL)) ||
max(decode(position,10,', '||substr(column_name,1,30),NULL)) ||
max(decode(position,11,', '||substr(column_name,1,30),NULL)) ||
max(decode(position,12,', '||substr(column_name,1,30),NULL)) ||
max(decode(position,13,', '||substr(column_name,1,30),NULL)) ||
max(decode(position,14,', '||substr(column_name,1,30),NULL)) ||
max(decode(position,15,', '||substr(column_name,1,30),NULL)) ||
max(decode(position,16,', '||substr(column_name,1,30),NULL)) columns
from user_cons_columns a, user_constraints b
where a.constraint_name = b.constraint_name
and b.constraint_type = 'R'
group by substr(a.table_name,1,30), substr(a.constraint_name,1,30) ) a,
( select substr(table_name,1,30) table_name, substr(index_name,1,30) index_name,
max(decode(column_position, 1, substr(column_name,1,30),NULL)) ||
max(decode(column_position, 2,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position, 3,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position, 4,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position, 5,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position, 6,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position, 7,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position, 8,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position, 9,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position,10,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position,11,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position,12,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position,13,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position,14,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position,15,', '||substr(column_name,1,30),NULL)) ||
max(decode(column_position,16,', '||substr(column_name,1,30),NULL)) columns
from user_ind_columns
group by substr(table_name,1,30), substr(index_name,1,30) ) b
where a.table_name = b.table_name (+)
and b.columns (+) like a.columns || '%';
|
] 
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