#include <db_cxx.h> int DbEnv::get_mp_mmapsize(size_t *mp_mmapsizep);
         The DbEnv::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 DbEnv::set_mp_mmapsize()
         method.
    
         The DbEnv::get_mp_mmapsize() method may be called at any time during
         the life of the application.
    
         The DbEnv::get_mp_mmapsize() 
            
            
                method either returns a non-zero error value or throws an
                exception that encapsulates a non-zero error value on
                failure, and returns 0 on success.