Good questions. I think it is 254 but I am not sure. Instructions on how to find the exact number you may find on page 114 of the O'Reilly's book Oracle Net8.
And yes, 10 dispatchers is too much. One dispatcher can handle all these 254 connections.
There is one interesting thing about dispachers I came to: They choose their own port. If you have firewall and only 1521 is open for thr listener, then you will get only dedicated connections although you think you have configured MTS. With firewalls the situation is a bit more complicated, you will have to have a separate init.ora parameter for each dispatcher. But that's another story....
I'm at a new site, and getting a crash course in MTS. I believe the MTS configuration needs some work.
The LARGE_POOL_SIZE is set to 0. In another thread on the site, one of th Sams recommends 10mb per server process. I have searched Oracle docs, but cannot find a method to calculate the size of the Large Pool.
Besides preventing fragmentation of the Shared Pool, what are the advantages of using the Large Pool for MTS?
One more question. We seem to have a lot of LOCAL connections. Does it imply that the MTS feature is not in use?