#include <db.h>

int
DB_ENV->get_mp_mmapsize(DB_ENV *dbenv, size_t *mp_mmapsizep);  

The DB_ENV->get_mp_mmapsize() method returns the the maximum file size, in bytes, for a file to be mapped into the process address space. This value can be managed using the DB_ENV->set_mp_mmapsize() method.

The DB_ENV->get_mp_mmapsize() method may be called at any time during the life of the application.

The DB_ENV->get_mp_mmapsize() method returns a non-zero error value on failure and 0 on success.