Hi Luiz,
In which config file can I to set MAINMEM value?
Please check out our documentation for more details (e.g. [1]).
Besides, I need to know if the system do the pagination automatically on the cases where main memory capacity is lower than the database size.
I am not sure what do you mean by "pagination", but probably the answer is "no": If main memory is not large enough, you will have to resort to disk-based processing. However, identical keys will only be referenced once in main memory, and the representation is much smaller than traditional DOM instances, so it's probably best if you simply give it a try.
Hope this helps, Christian