#include <db_cxx.h> int DbEnv::set_memory_max(u_int32_t gbytes, u_int32_t bytes);
        This method sets the maximum amount of memory to be used by shared
        structures in the main environment region.  These are the
        structures used to coordinate access to the environment other than
        mutexes and those in the page cache (memory pool).  If the region
        files are in memory mapped files,  or if
        DB_PRIVATE is specified, the memory specified by
        this method is not allocated completely at startup.  As memory is
        needed, the shared region will be extended or, in the case of
        DB_PRIVATE, more memory will be allocated using
        the system malloc call.  For memory mapped files, a mapped region
        will be allocated to this size but the underlying file will only be
        allocated sufficient memory to hold the initial allocation of
        shared memory structures as set by
	DbEnv::set_memory_init().
    
        If no memory maximum is specified then it is calculated from
        defaults, initial settings or (deprecated) maximum settings of the
        various shared structures.  In the case of environments created
        with DB_PRIVATE, no maximum need be set and the
        shared structure allocation will grow as needed until the process
        memory limit is exhausted.
    
The database environment's maximum memory may also be configured using the environment's DB_CONFIG file. The syntax of the entry in that file is a single line with the string "set_memory_max", one or more whitespace characters, followed by the maximum to be allocated. Because the DB_CONFIG file is read when the database environment is opened, it will silently overrule configuration done before that time.
         The DbEnv::set_memory_max() method must be
         called prior to opening the database environment.
    
                The DbEnv::set_memory_max() 
            
            
                method may fail and throw a DbException 
                exception, encapsulating one of the following non-zero errors, or return one
                of the following non-zero errors:
            
        
            
If the method was called after DbEnv::open() was called; or if an invalid flag value or parameter was specified.