Array Fetch Size limitations

Hi All,

My environment:

BO 3.1 SP 6

Database Oracle 11g

my issue is, i am working on transactional database, there are billions of rows. I need to show the counts of those in my reports, its taking forever to returning the results(almost 3+ hours)

I am thinking to increase the array fetch size but not sure what the ideal limit is. Can some one help in this.

Current Array Fetch Size is 250 and Array bind size is 32767 can i increase the fetch size to 500 or 1000?

Thanks,

Praveen.