We are using 6 instances....

We have been able to create 5 different Oracle instances under a single Oracle Home installation and all the 5 instances run successfully at the same time.
But the problem arises when we create 6th instance. At this period, Oracle seem to corrupt all the other instances also.

To create the databases, we are using "create database" syntax.

What could be the maximum number of tables which can be created in a single instance or database ? What could be the amximum size of a table ?

Thanks for the help.....