Best way to use Activation Groups

Hi all,

What is the best way to use Activation groups? I am really worried about
file access.

I have a lot of Utility procedures with core business logic that is right
now repeated in most of the programs.
I am trying a progressive approach as to when ever we change a particular
program find the generalizable procedures and put it in a service program.
Change the program to use these procedures. Also I have made all the utility
Service Programs to run in one activation group.

The major question I have is:

Should I use it with OVRDBF ..... Share(*YES) ? What are the advantages over
not using  Share(*YES)

Also how do I control open and close of files.. I do not want to open and
close a file each time a procedure is called.

Please advice and let me know any good resources to look at.


Thanks & Regards
Praveen