update enque deque

HI

I need to update two database tables using update statement .

I know enque deque is needed before update modify etc operations with databse tables

my question is if enque deque is not used what is the performance impact and implications ( the database table is locked so that multiple user performing same operations or using same database update application does not results in conflicts ) but I have checked in backend only once the application is executed fully the update is done for eg first update return is sy-subrc = 0 (in debugging mode ) and second update statement is executed only when the program is closed and run full the update to database is visible in data base elsewise the update is not done even if first update on first table has sy-subrc = 0.

also update statement locks the database tables automatically as checked in sm12 so is there need for enque deque really or it is just a performance and code review practice.

pls suggest

regards

Nishant