I want know are there in trade offs in having BMP and CMP in same application. Also considering scenerio that, there may be a BMP Entitiy Bean updating a database table which is also referred by a CMP Entity Bean. Type of CMP Entity Bean can be read/write or read only in this case.

I would encourage you to use CMP as much as you can.

I agree with Eric. CMP is are very convenient to develop and most of the time it is efficient.

To answer your question. There should not be any problem with a BMP modifying the row which is being referred by a CMP assuming that CMP implementes version pattern.

Version pattern is necessary in following scenario -
CMP refers to a data row
BMP updates that row
CMP updates the data using using the stale data

In Weblogic 6.1, the default behaviour is when ever a business method is called on the CMP, container does the following
1. refreshes the data from the database
2. executes the business method
3. updates the database.