How to use commit work as per the requirement?

Hi all,

Here i have a requirement about database table updation. I have to update a database table, at the time of doing commit work it has to check the following condition .

The data should be split up in different groups or records of no more than 2000 after which a commit to the database is executed.

So can anybody help me in this regard with a piece of code? and i want to know during updation how to lock the data base table and how to unlock? Is there any standard function modules to call regarding this locking and unlocking?

Thanks & Regards

Naidu