Hello
I would recommend moving to DP8. The database technology was changed to a much more performing one. You will be able to store 50 times more data in it and have good performances.
From DP 6.11, it's a one step. No need to go to DP7.
If you can't upgrade, you will have to install a new Cell Manager to split the load. You can share a library between them if you get the Manager of Manager (MoM) option.
Regards
JM