I have a table with 7 foreign keys.
How can I drop then and again add them to a table in DB2?

ALTER TABLE DROP FOREIGN KEY

ALTER TABLE ADD FOREIGN KEY

Look them up in the manual.

Andy

db2look with drop option could help
db2look - DB2 Statistics and DDL extraction tool command

Are there any disaadvantages of dropping the foreign keys from the table.
Then deleting all the data from parent table and child table and then again adding the foreign keys.
As by this way it reduces my time of deletion of records from Parent table.
Also if there are any disadvantages in doing so, is there any other way to do the same.

what is the purpose of the test / operation and what are you trying todo
please explain clearly whit details.. we can not see what you are thinking..

I have two tables Parent table and the Child table.
The Child table has foreign keys refering to the Parent table.
Both the tables contain around 1 lack rows, now I want to delete all the rows in both the tables.
It takes around 1 min for the Child table to be cleared but for Parent table it takes 30 minutes.
So I dropped the Foreign key relation and then the Parent table is also cleared in 1 min.
Then I again assign the foreign keys to the child table before a fresh insertion.
So is this thing has any disadvantages, and is there any other way to perform the above steps. I also tried CASCADE ON DELETE for Child table but then also it is taking 30 minutes to delete the data from both the tables.

I would : take db2look - remove foreign keys - clear tables with truncate command or load from /dev/null - reload data - re-execute db2look.. depending on the size and nbr of indexes.. indexes can be dropped or kept during the load

To drop a FOREIGN KEY constraint, use the following SQL:

MySQL:
ALTER TABLE Orders
DROP FOREIGN KEY fk_PerOrders

SQL Server / Oracle / MS Access:
ALTER TABLE Orders
DROP CONSTRAINT fk_PerOrders