usropn files and service programs

hi,

i got a procedure in a service program which might be called once in a
session f. e. in a maintenance program or  ten million times in a batch
program.

afaik the default advice of ibm is that files in a service program
should be defined usropn. but if i open and close the files on every
procedure call the batch program is really slow.

my solution would be to make at least three procedures in the service
program:
openFiles()
action()
closeFiles()

my batch program would look like this:

openfiles();

dow (xxx);
   ...
   action();
   ...
enddo;

closeFiles();

afaik if the service program is compiled with actgrp(*caller) and the
calling program is running in its own activation group the program
should run as expected.

is there any error in my way of thinking and are there any other
(better) solutions to this? i think this is quite a common problem and
probably everyone has faced this problem and found a solution. so i
would like to here your solutions.

thanx in advance

mk