Select for update statements

 
Hi,

While investigating one of our database supporting a home grown application, we found out that in he shared pool
there are 2 types of statments involving updates

First one is --> update <table Name> set <col1> = value
Second one is --> select <col1> from <table Name> where ....for update

Could someone please shed some light into as to what the second update statement is meant to accomplish and
what could be the purpose of such statement?

Are there any downsides of using these type of "For UPDATE" statements?

What is Oracle's take on these type of statements?


Thanks