guys can somebody please get me information on db2 internal functions because they are required to study db2diag.log file

What do you mean by "internal functions". Also state DB2 version and OS.

Andy

What would you need to know internal functions for understanding the db2diag.log?

You can check the notify log (*.nfy) instead. But you don't really need to know the function names in order to understand the information in the db2diag.log. Knowing the component (ie. data management, database utilities) should be sufficient.