It sounds like you may have a design issue. In a well-designed, normalized database, you should not have a lot of repeating data, especially if you have "groups" of repeating data that is often the same. You should break out the data into multiple table that make sense.
For example, let's say that you have a group of employee information, i.e. First Name, Last Name, Address, Phone Number, Age.
Instead of having this data repeat many times, you would have an employee table, when this information is entered once.
Then, you just link this table to other tables, queries, etc.
On Forms, you may have a lookup to the employee table, where when you select an employee, it brings up all this information (though it does not really add it or store it in any new table records).
Does that sound like something like what might be going on?
Also, I am not sure what you mean by "These forms are not open at the same time". Forms, per se, don't "hold" any data. They just display data that resides in tables/queries, or are used to enter data into a table.
An unopened Form would not hold any data.